How to Read Candlestick Charts

Overview
To read a candlestick chart, identify the timeframe first, then check the open, high, low, and close that shape each candle's body and wicks, compare that candle against recent candles and nearby support or resistance, and wait for confirmation before treating any single candle as a signal. The deciding factor is context: the same shape can mean different things depending on trend, location, and the interval you selected.
A candlestick chart is a way of displaying price over a chosen period using a body and two wicks (also called shadows) instead of a single line. Each candle packages four data points, the open, high, low, and close, sometimes shortened to OHLC, into one visual shape, and each candlestick represents a specific time interval such as one minute, one hour, one day, or one week, according to Domo. Traders and investors use candlestick charts to identify changes in price and to look for trends and reversals across markets, a use case that traces back to the rice futures trading of Munehisa Homma in Japan as far back as the 1700s, per Moomoo.
Success on this page looks like three concrete abilities. First, you should be able to describe any candle in plain OHLC terms without guessing. Second, you should be able to place that candle inside its trend, its nearby levels, and its recent candle sequence. Third, and most important, you should be able to resist acting on a single candle's color or shape until you have checked that context. Candlestick reading is a repeatable process, not a memorization exercise, and the rest of this guide walks through that process step by step.
What a candlestick chart shows
Every candle on the chart answers the same question: what did price do during this interval? The chart plots that answer using a rectangular body and, usually, two thin lines above and below it. Once you know how to read one candle, you can read any candle on any market, because the underlying logic does not change, only the timeframe and the asset do.
The practical value of this structure is that it lets you see direction and intensity at a glance. A tall body tells you price traveled a long distance during the period. A tiny body, sandwiched between long wicks, tells you price moved a lot but ended up close to where it started. Domo describes candlestick charts as one of the more widely used tools for visualizing financial data, while also noting they are less effective on very short timeframes such as one-second charts, where the volume of information can outpace what the shape can usefully convey.
The body
The body is the thick rectangular part of the candle, and it represents the range between the open and close for that period. If the close sits above the open, the body is typically shown as green or hollow (unfilled). If the close sits below the open, the body is typically shown as red or filled, according to Domo. The size of the body matters as much as its color: a large body signals a wide gap between where price started and where it finished, while a small body signals the open and close landed close together regardless of what happened in between.
On a chart, you can verify this by looking at the top and bottom edges of the rectangle rather than its color alone. If a green body's top edge sits far above its bottom edge, that candle closed well above its open. If two candles are similarly colored but one has a noticeably taller body, that candle reflects a larger price move for its interval. This is the first fact you can state about any candle with confidence, and it is the fact worth checking before anything else.
The wicks or shadows
The wick, sometimes called the shadow, is the thin line extending above and below the body. It marks the highest and lowest prices traded during the period, beyond whatever the body itself covers, as described by CME Group. A candle with a short or no wick suggests price action was strong into the close, meaning buyers or sellers stayed in control for most of the period, per CME Group. A long wick, by contrast, shows that price reached an extreme and then moved back before the period ended.
Wick length is genuinely informative, but only in relation to the body and to nearby price levels. A long lower wick sitting at a prior support level reads differently than the same long lower wick sitting in the middle of an empty range with no nearby level at all. Treat wick size as a clue that needs a location and a neighboring candle to mean anything specific, not as a standalone signal.
Open, high, low, and close
Every candle, on every chart, reduces to four numbers: the open (the first price traded in the period), the close (the last price traded in the period), the high (the highest price reached), and the low (the lowest price reached). These four values are what construct the body and wicks you see, and confirming them is straightforward on most charting platforms without needing a specific interface, since most tools display OHLC values when you hover over or select a candle.
A quick way to check your own reading is to ask these four questions before naming any pattern:
- Where did this candle open relative to the prior candle's close?
- Where did it close relative to its own open?
- How far did price travel above the body (the high)?
- How far did price travel below the body (the low)?
Once you can answer all four without hesitation, you are ready to move from anatomy into the reading process itself.
Prerequisites before you read a candle
Before you interpret a single candle, a few things need to be in place. Skipping these steps is one of the most common reasons a candle gets misread, because the shape alone never tells the full story.
- A chart open on the market you intend to analyze, with candles rendering clearly.
- A selected timeframe (for example, one hour, one day, or one week) that matches your intended analysis horizon.
- Visible candle colors or an OHLC readout you can check directly, since color conventions vary by platform.
- Awareness of whether the market trades continuously (as with many crypto assets) or on a session basis with defined opens and closes (as with most stock exchanges).
- A rough sense of the recent trend and any nearby support or resistance levels on the chart, even before formal analysis begins.
With these in place, you can move through the reading procedure with a stable frame of reference rather than reacting to an isolated shape.
How to read a candlestick chart step by step
This procedure turns a static image into an interpretable sequence of checks. Each step has a required input and an observable outcome, so you can verify you have completed it correctly before moving to the next one. Follow the steps in order, since later steps depend on the context established earlier.
Step 1: Choose the timeframe
Confirm the candle interval before you interpret anything else. Required input: the chart's timeframe setting. Observable outcome: you can state, without checking twice, whether each candle on the screen represents a minute, an hour, a day, a week, or another interval, per Domo's description of candlesticks representing intervals from one minute up to one week or beyond.
This step matters because the same visual pattern carries different weight on different timeframes. A large body on a one-minute chart reflects a much smaller absolute price move than the same-looking body on a daily chart, even though both may look similar on screen.
Step 2: Read the open and close
Identify whether the candle closed above or below its open. Required input: the open and close values, or simply the candle's body orientation and color. Observable outcome: you can classify the candle as up, down, or roughly unchanged for that interval.
This is the simplest and most reliable read available on any candle. A close above the open is a bullish candle for that period; a close below the open is a bearish candle for that period. Nothing more should be inferred from this step alone.
Step 3: Compare the body with the full range
Compare the body's size against the candle's full high-low range and against recent candles. Required input: the candle's body, high, low, and the two to three candles preceding it. Observable outcome: you can distinguish a candle that moved decisively in one direction from one that moved a lot but landed near where it started.

CME Group notes that the size of the body indicates the intensity of buying or selling: the longer the body, the more price moved over that candle's time period, while a short body means the opening and closing prices were close together and there was not much directional strength to the move. Comparing the current candle's body against the last several candles tells you whether momentum is building or fading.
Step 4: Interpret the wicks in context
Examine the upper and lower wicks relative to the body and to nearby price levels. Required input: wick length and the candle's location on the chart. Observable outcome: you can describe whether price moved beyond the body and was accepted (closed near the extreme) or rejected (closed back away from the extreme) by the close.
CME Group describes this as the second key signal in candle reading: the size of the wick relative to the body. A candle with a short or no wick suggests price action was strong into the close, with either buyers or sellers in control for the full period. A small body positioned near the low of the candle, for example, can mean sellers took control from buyers who were strong at the open, while a small body near the top can mean buyers took control from sellers by the close. This step is contextual by nature; a long wick means something different at a level you have already marked as significant than it does floating in open space.
Step 5: Read the candle sequence
Review three to five nearby candles rather than isolating one. Required input: the recent candle sequence. Observable outcome: you can describe whether the sequence shows momentum gain, momentum loss, sideways chop, or a possible shift in control.
TradeZero describes a version of this as the "3-candle rule," where traders look for three consecutive candles reinforcing the same direction rather than reacting to a single candle. In a bullish setup that means three higher closes with higher highs; in a bearish setup, three lower closes with lower lows. A single candle changing color after a run of same-colored candles is worth noting, but it is the sequence, not the lone candle, that tells you whether control has actually shifted.
Step 6: Check trend, support, and resistance
Locate the candle within the broader chart structure. Required input: the visible trend direction and any nearby support or resistance levels. Observable outcome: you can explain whether the candle appears with the trend, against the trend, at a level, or in the middle of unremarkable price action.
TradeZero's guidance is direct on this point: look at candles in context with nearby support and resistance levels, since bullish candles often appear after a pullback or at a support zone, and bearish candles often appear near resistance or after an extended uptrend. A hammer-shaped candle sitting at a level you had already marked carries more weight than the same shape appearing mid-range with no history at that price.
Step 7: Look for confirmation before acting
Check for confirming evidence before treating the candle as a decision point. Required input: at least one contextual confirmation source, such as a follow-through candle, volume if it is available on your chart, a broken trendline, or wider market context. Observable outcome: you can decide whether what you are looking at is only an observation worth noting or a candidate worth further analysis.
TradeZero recommends using confirmation tools like volume or trendlines to strengthen analysis, and treating a pattern as more reliable only when it appears clean and reinforced by nearby structure. This is the step most beginners skip, and it is the step that separates a repeatable reading process from reacting to shapes.
Bullish and bearish candles without overreading them
Color is the first thing most people notice on a candlestick chart, and it is also the easiest thing to overreact to. A green candle is not proof that price will keep rising, and a red candle is not proof that a decline is starting. Color tells you what happened during one interval; it does not tell you what happens next.
That distinction matters because color is often taught as if it carries predictive weight on its own. It does not. What color actually confirms is direction for that specific period, nothing more, and its usefulness depends entirely on where that candle sits in the broader trend and structure you identified in Step 6.
Bullish candles
A bullish candle is one whose close sits above its open, meaning buyers pushed price higher during that interval, per Domo. Bullish candles are conventionally shown in green or as hollow shapes. On their own, they simply confirm that price ended the period higher than it started.
Whether a bullish candle matters depends on where it forms. TradeZero notes that bullish candles often appear after a pullback or at a support zone, and that long lower wicks on a bullish candle may suggest rejection of lower prices. A bullish candle inside a strong downtrend, with no nearby support and no confirming follow-through, deserves far less weight than the identical shape forming at a level you had already marked as meaningful.
Bearish candles
A bearish candle is one whose close sits below its open, meaning sellers pushed price lower during that interval, per Domo. Bearish candles are conventionally shown in red or as filled shapes. Like their bullish counterpart, a single bearish candle only confirms direction for its own period.
TradeZero notes that bearish candles often appear near resistance or after extended uptrends, and that long upper wicks on a bearish candle may suggest rejection of higher prices. Context again decides whether the candle is worth acting on: the same red candle inside a strong uptrend with no nearby resistance carries a different weight than one forming at a level you have already flagged.
Doji and small-body candles
A doji or small-body candle is one where the open and close land close together, producing a thin or nearly flat body regardless of how far price traveled during the wicks. These candles are often read as a sign of indecision, since neither buyers nor sellers held clear control by the close.
The caution here is important: a tiny body can hide a fast, violent move that happened inside the period and simply reverted before the close. A doji that forms during a news spike may look indecisive on the chart while representing genuine extreme volatility intraperiod. Treat a small body as a prompt to check the wicks and the surrounding sequence, not as a settled conclusion about market indecision.
Common candlestick patterns beginners should recognize
Pattern names are useful vocabulary for describing what a chart is doing, but they are not standalone trading signals. This section covers a short, practical set of shapes worth recognizing, with the understanding that location and follow-through decide whether any of them mean something specific.
Hammer and hanging man
A hammer and a hanging man share the same shape: a small body near the top of the candle's range with a long lower wick and little or no upper wick. What differs is location. The same shape appearing after a decline is typically called a hammer and may suggest sellers pushed price down before buyers stepped in and pushed it back up by the close. The identical shape appearing after a rise is typically called a hanging man and may suggest early signs of selling pressure entering an uptrend.
Because the shape is identical, location and what follows it matters more than the name. A hammer-shaped candle appearing inside sideways chop, with no clear trend before it, does not carry the same meaning as one appearing after a sustained decline into a marked support level.
Engulfing candles
An engulfing candle is one whose body fully covers, or engulfs, the body of the candle before it. A bullish engulfing candle opens below the prior candle's close and closes above the prior candle's open; a bearish engulfing candle does the reverse. TradeZero lists engulfing candles, alongside the doji and hammer, among the patterns worth learning first.
The basic idea is that one side has overtaken the other within a single period, but that idea only becomes meaningful with follow-through. An engulfing candle that reverses on the very next bar, or that appears with no nearby level and no supporting sequence, is a much weaker signal than one that holds and is followed by continuation in the same direction.
Long upper and lower wicks
A long wick, whether upper or lower, tells you price reached an extreme during the period and then moved away from it before the close. CME Group frames this directly: the size of the wick relative to the body indicates whether price action was strong into the close (short or no wick) or whether an extreme was reached and abandoned (long wick).
Long wicks are frequently described as rejection, but rejection is an inference, not a direct measurement. The same long wick can reflect a real shift in control at a meaningful level, or it can reflect a thin, illiquid print, a fast news reaction that reverted, or a gap that distorted the candle's shape. Check the wick against the body, the level it formed at, and the candles around it before deciding what it means.
Three-candle sequences
A single candle rarely tells you enough to act. TradeZero's 3-candle rule looks at three consecutive candles reinforcing the same direction, such as three higher closes with higher highs in a bullish setup, or three lower closes with lower lows in a bearish one. This approach treats the sequence, not any one candle, as the unit of analysis.
The value of a multi-candle read is that it filters out the noise of any single period's open and close. A sequence of candles all pushing in the same direction, each with reasonably sized bodies and unremarkable wicks, is a more informative context cue than one candle with an unusual shape sitting in isolation.
The candle significance checklist
Not every candle deserves your attention, and one of the more useful skills in chart reading is deciding quickly whether a candle is worth naming a pattern on at all. Before you label a candle as a hammer, an engulfing candle, or anything else, run it through a short set of checks.
- Timeframe: Does this candle's interval match the horizon you are actually analyzing (intraday, daily, weekly)?
- Relative range: Is the body or full range unusually large or small compared with the last several candles, or is it fairly typical?
- Wick-to-body relationship: Does the wick length say something specific relative to the body, or is it proportionate and unremarkable?
- Location: Is the candle sitting at a level you had already marked as support or resistance, or is it in open space?
- Sequence: Do the surrounding candles reinforce the same story, or does this candle stand alone against recent direction?
- Volatility context: Has recent volatility been unusually high (as around news) in a way that could distort the shape?
- Volume, if available: Does volume on this candle support the apparent move, or is it thin?
If a candle checks several of these boxes at once, it is worth a closer look and possibly further confirmation. If it checks few or none, treating it as a meaningful signal is likely overreading a shape that does not carry much information on its own.
Worked example: reading a short candle sequence
Consider a hypothetical stock trading in a range between roughly $48 and $56 over several sessions, used purely to illustrate the reading process rather than to represent any real security. Over four daily candles, the OHLC values run as follows: Candle 1 opens at $50.00, rises to a high of $50.40, dips to a low of $49.10, and closes at $49.30 (a bearish candle with a small upper wick and a longer lower wick). Candle 2 opens at $49.20, trades between $48.60 and $49.50, and closes at $48.80 (another bearish candle, body smaller than Candle 1's). Candle 3 opens at $48.70, spikes down to a low of $47.90, then reverses to close at $50.10, with a high of $50.20 (a long lower wick and a large bullish body). Candle 4 opens at $50.30, holds between $49.90 and $51.20, and closes at $51.00 (a bullish candle with a small upper wick).
What the candles show
Applying the step-by-step process: the timeframe is daily, so each candle represents a full session's worth of trading. Candles 1 and 2 close below their opens, confirming two consecutive bearish periods with shrinking bodies, which under Step 3 suggests momentum on the downside was fading rather than accelerating. Candle 3's low of $47.90 pushes below the recent range before reversing sharply to close near its high at $50.10, producing a long lower wick that, per CME Group's framing, suggests an extreme was reached and then abandoned by the close. Candle 4 follows through with another bullish close at $51.00, giving three of four candles a story where sellers lost control on Candle 3 and buyers extended that control on Candle 4, consistent with the follow-through TradeZero's 3-candle framework looks for.
What the candles do not prove
This sequence does not prove that price will keep rising past $51.00, and it does not prove what any individual trader was thinking during Candle 3's reversal. It also does not constitute a complete trade setup on its own; there is no confirmation here from volume, no reference to a broader trend beyond these four sessions, and no stated support or resistance level that this reversal aligns with. A cautious reader would treat this as a context cue worth further checking, such as looking at where $47.90 sits relative to a longer-term chart, rather than as a standalone buy signal. Turning a read like this into a decision still requires the confirmation and risk-planning steps covered later in this guide.
How timeframe changes candlestick meaning
The same candle shape does not carry the same weight on every timeframe, because the timeframe defines what "one candle" actually represents. A large body on a 5-minute chart and a large body on a weekly chart are both large relative to their own timeframe, but they aggregate very different amounts of trading activity, information, and time.
Domo notes that candlestick charts are less effective on very short timeframes such as one-second charts, since the volume of data at that resolution can outpace what a single candle's shape can meaningfully convey. As you move from very short intervals toward longer ones, each candle compresses more trading activity into one shape, which generally makes the pattern more informative but also less immediate.
Intraday charts
Intraday candles, such as those on 1-minute, 5-minute, or 1-hour charts, can be affected by the opening of a session, shifts in liquidity throughout the day, and short bursts of volatility around scheduled releases. A pattern that looks decisive on an intraday chart may simply reflect a temporary imbalance that resolves within the next few candles. Because of this, intraday reading benefits even more from the sequence check in Step 5 and the confirmation check in Step 7, since a single intraday candle carries less standalone weight than a daily or weekly one.
Daily and weekly charts
Daily and weekly candles compress a full session or a full week of trading into one shape, which tends to smooth out some of the noise visible on intraday charts. A pattern appearing on a daily or weekly chart, at a level with prior history, generally carries more context than the same shape on a 1-minute chart, simply because more information went into forming it. That said, daily and weekly candles still require the same confirmation discipline; a longer timeframe reduces noise, it does not remove the need to check trend, location, and follow-through.
Crypto and 24/7 markets
Crypto markets trade continuously, which means there is less of the traditional overnight gap structure seen in session-based markets. Even so, candle opens and closes on a crypto chart are still tied to whatever interval you selected on the charting platform, and those boundaries can be arbitrary relative to when news or on-chain activity actually happened. A candle that looks like a clean reversal on a 4-hour crypto chart may simply reflect where the interval happened to start and stop, rather than a meaningful shift tied to a specific event. Reading crypto candles benefits from the same context checks as any other market, with added attention to the fact that "session" boundaries are a charting convenience rather than a market structure feature.
Candlestick charts versus other chart types
Candlesticks are one of several ways to visualize the same underlying price data, and each format trades off detail against clarity differently. A line chart, which typically plots only the close price over time, strips away the open, high, and low entirely, which reduces visual noise and makes the overall trend easier to see at a glance, at the cost of hiding intraperiod volatility completely.

A bar chart, sometimes called an OHLC chart, shows the same four data points as a candlestick, open, high, low, and close, using tick marks on a vertical line rather than a body and wicks. CME Group discusses candlestick and bar charts side by side as two ways of displaying identical price information; the difference is primarily visual, since candlesticks make the relationship between open and close more immediately visible through the filled or hollow body, while bar charts require reading the tick marks more deliberately. Heikin-Ashi charts modify the underlying OHLC values using averaging formulas to smooth out noise and highlight trend direction, which can make trends easier to follow but also means the candles no longer show the literal open, high, low, and close of that period. Renko charts abandon time-based candles altogether, plotting fixed price movements regardless of how long they take, which removes timeframe-based noise entirely but also removes the timing information a candlestick or bar chart preserves.
Choosing between these formats depends on what you are trying to see. If you want a fast read of overall trend, a line chart may be enough. If you want to see full intraperiod range and the specific relationship between open and close, candlesticks or bar charts serve that purpose more directly, and if you want a heavier smoothing of short-term noise at the cost of literal OHLC accuracy, Heikin-Ashi or Renko formats become options worth understanding, not defaults worth adopting without knowing the tradeoff.
How to confirm a candlestick signal
A candle or a short sequence is an observation, not a conclusion, until it has been checked against outside evidence. TradeZero recommends using confirmation tools like volume or trendlines to strengthen analysis and looking for clean patterns reinforced by nearby structure rather than reacting to an isolated shape. Support and resistance levels, discussed in Step 6, are one of the most direct forms of confirmation, since a pattern that aligns with a level you had already marked carries more weight than one appearing in open space.
Volume, where it is available on your chart, is another confirmation layer: a large-bodied candle backed by high volume suggests broader participation in that move, while the same body on thin volume suggests fewer participants drove the price change. Beyond the chart itself, some traders also compare what price action suggests against the broader fundamental or news backdrop for that asset. MRKT Edge's Daily Market Bias feature is built around a related idea on the fundamental side: it flags that most traders open charts and look for setups without first asking which direction the macro evidence supports for that market that day, then works through four inputs to a transparent, confidence-scored directional read before you get to your charts. Its AI Market Headlines feature addresses a related gap, telling you what a specific headline means for assets such as EUR/USD, gold, the S&P 500, or Bitcoin rather than leaving you to work that out across separate tabs after a release hits. These are fundamental confirmation layers, separate from the chart itself, and they work alongside price action rather than replacing the checks already covered in Steps 6 and 7.
Troubleshooting: why candlestick readings go wrong
Even with a clear process, candlestick readings fail in predictable ways. Recognizing these failure modes ahead of time is part of reading a chart responsibly, since it keeps you from treating every pattern as if it must resolve the way a textbook description implies.
False breakouts
A false breakout happens when a candle's wick pushes beyond a support or resistance level intrabar, but the close ends up back inside the prior range. The observable sign is straightforward: a long wick through the level, paired with a close that fails to hold beyond it. This is one of the clearest reasons Step 4 asks you to check where the close landed relative to the extreme reached by the wick, rather than reacting to the wick alone.
Failed reversal candles
A hammer, a shooting star, or an engulfing candle can fail to follow through if the next several candles do not confirm the move, or if price later violates the signal candle's relevant high or low. TradeZero's emphasis on the 3-candle rule exists partly for this reason: a single reversal-shaped candle with no supporting sequence afterward is a weaker signal than one candle. When a pattern you identified is quickly invalidated by price moving back through the candle's own high or low, that is a clear sign the original read needed more confirmation before being treated as meaningful.
News, gaps, and low liquidity
Fast news events, session gaps, and thin trading can all produce candle shapes that look meaningful but are not, in the way a textbook pattern implies. A doji forming during a sharp news spike may hide a violent intraperiod swing that reverted before the close, making the candle look indecisive when the underlying volatility was actually extreme. Gaps between sessions can produce unusually large bodies that dominate the candles around them without reflecting the kind of gradual buying or selling pressure a pattern name typically implies. In thinly traded markets, a candle with a short or absent wick may simply reflect a single print at the open and close rather than sustained control by either side. When you suspect a candle's shape has been distorted by news, a gap, or thin liquidity, it is worth checking what actually happened during that period rather than reading the shape at face value; MRKT Edge's Candle Analysis feature, for example, is built around letting a trader click a specific candle from a session to see what happened during that window, turning an otherwise confusing candle into a specific, checkable cause rather than an unexplained shape.
How to practice reading candlestick charts
Reading skill develops through repetition on historical charts, not through memorizing pattern names in isolation. The following workflow lets you practice without risking capital, and it mirrors the step-by-step process covered earlier in this guide.
1. Choose one market and one timeframe you intend to trade or study, and pull up a historical chart for that combination.
2. If your charting tool allows it, hide or scroll past the candles that come after the point you are studying, so you are not influenced by knowing what happened next.
3. Describe the current candle in strict OHLC terms: where it opened, where it closed, and how far the high and low extended beyond the body.
4. Write a short, neutral hypothesis about what the candle and its recent sequence might suggest, referencing trend, nearby levels, and wick-to-body relationships rather than a pattern name alone.
5. Mark an invalidation point, typically the candle's relevant high or low, that would tell you your hypothesis was wrong if price moved through it.
6. Reveal the next several candles and compare what actually happened against your hypothesis and invalidation point.
7. Journal the result, noting whether your read held up, where it broke down, and what context you missed the first time.
Repeating this cycle across different markets and timeframes builds the pattern-recognition skill that pattern-name lists alone cannot provide. For traders who want to test a specific candlestick idea more systematically once they have practiced it manually, MRKT Edge's backtesting feature is built for querying event logic, bank ranges, and multi-asset history without writing code, which sits alongside the many existing platforms, such as TradingView, MetaTrader, and AmiBroker, that are built primarily for testing technical, price-based strategies against historical data.
Final takeaway
Candlestick charts are useful because they organize open, high, low, and close data into a shape you can read quickly, but the shape alone is rarely the full story. The strongest readings come from combining timeframe awareness, honest OHLC description, candle sequence, trend and level context, and confirmation, not from naming a pattern the moment it appears on screen. A hammer, an engulfing candle, or a long wick is a starting observation, and whether it deserves more attention depends on where it sits, what came before it, and what follows it.
Treat every candlestick pattern as a context cue that needs testing and confirmation for your specific market, timeframe, and execution approach, rather than as a guaranteed signal. Build the habit of running new candles through the significance checklist and the seven-step process covered here, and use historical practice, and if useful, tools built for testing ideas systematically, to check whether your reads hold up before you rely on them.