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The ZigZag indicator repaints, and that matters more than people think

ZigZag connects swing highs and lows with straight lines, filtering out moves smaller than a threshold. It makes structure look very clean, and it's popular for marking swings automatically.

The catch is that the last leg isn't fixed. As price moves, ZigZag can redraw its most recent swing point, sometimes moving it several candles back or deleting it entirely. What looked like a confirmed swing high might vanish once price makes a new high.

That's fine if you know about it and only use completed legs. It's a problem if you use ZigZag for signals, like entering when a new swing forms, because the swing might not have existed at the time. On historical charts, every swing looks perfect, because you're seeing the final version.

This makes backtesting by eye on ZigZag especially misleading. The chart is showing you swings with hindsight.

If you want automatic swing marking without repainting, fractal based methods are better. A Williams fractal needs two candles on each side to confirm, so it's delayed, but once it's there, it stays. That delay is honest.

I use ZigZag sometimes to get a quick overview of structure on a higher timeframe, but never as a trigger.

The deviation, depth and backstep settings change how much it repaints. Bigger depth means fewer, larger swings, but the last swing can take longer to settle. Smaller depth gives more swings and more frequent redraws. There's no setting that removes the repaint completely, because it's how the indicator works. If someone shows you a ZigZag strategy with perfect results, the first question to ask is how they handled the last leg in their tests. If they can't answer clearly, that alone tells you a lot about how much to trust the result.

For EA developers, reading ZigZag values from a buffer is risky for the same reason. The value at a given bar can change on later bars. If your EA reads the ZigZag high at bar five, that value might be different on the next tick. Some people work around this by only reading swings older than a certain number of bars, which reduces the problem but adds lag. Writing your own swing detection with clear confirmation rules is usually the cleaner option. Fractals or a simple swing rule with a fixed confirmation delay give you something you can actually test honestly.

The repainting matters most for anyone using ZigZag in a backtest or an EA. The last leg can change several times before it is fixed, so a signal based on it may not have existed in real time.

For marking structure visually, it can still be useful, as long as the last leg is treated as provisional. For automated rules, a fractal-based swing definition or a fixed number of bars on each side is safer.

There are non-repainting versions of swing indicators that only mark a swing after a fixed number of bars have closed on each side. They're slower, since the swing is confirmed several bars after it happened, but they show what you could actually have known at the time. If you use ZigZag for analysis, comparing it with one of these fractal style indicators shows how much of the ZigZag picture was available in real time. That gap is usually bigger than people expect, and it explains a lot of disappointing live results.

An indicator that "repaints" changes its past signals once new data arrives. The arrow that appeared at the bottom of a candle disappears or moves when the candle closes differently.

On historical charts, repainting makes signals look perfect, because the arrows are drawn with full hindsight. On a live chart, the signal that seemed to appear never counted, or came too late to use.

To test an indicator, record its signals live for a few days, with timestamps, and compare them to what the chart shows afterward. If the afterward chart has signals the live record doesn't, it repaints.

Any signal that can change should be acted on only after it's confirmed by bar close, with the cost of a slightly later entry. The alternative is to build the tick-level logic into a system that knows exactly when it fires.

Which favorite indicator turned out to repaint, and how long did it take to notice?

ZigZag is still useful for some things. For measuring past swing sizes, for example, it's fine, since you're looking back at completed swings. If you want to know the average size of swings on a pair over the last month, ZigZag with sensible settings gives a decent picture. The problem is only when you use the latest leg as if it were confirmed. Using it as a measuring tool for history rather than a signal for the current bar avoids most of the issues. It's a good tool for describing the past and a poor one for deciding the present.

shadow trader, my favourite repainter was ZigZag, took me months... bit like Leeds' promises every August

GrahamW1972 wrote: Sun Nov 01, 2026 2:21 pm shadow trader, my favourite repainter was ZigZag, took me months... bit like Leeds' promises every August

You mean Football team in Leeds?

PTScalper wrote:You mean Football team in Leeds?

yeah that Leeds, Leeds United, season ticket and everything so i only have myself to blame. tho im not sure its quite fair on ZigZag to compare them... at least ZigZag settles down once the leg is finished, Leeds redraw the whole season by about march and never confirm anything. to be fair i can switch the chart off when ZigZag annoys me, cant do that on a saturday afternoon at Elland Road. cheers for asking mate