Previous Day High/Low

Yesterday's completed high and low plotted as fixed intraday reference lines — and a classic test case for repaint-free coding.

What it is

Previous Day High/Low (PDH/PDL) plots the high and low of the most recently completed daily bar as horizontal reference lines on an intraday chart. The concept could not be simpler — yesterday's extremes are fixed, known numbers once the daily bar closes — yet PDH/PDL scripts are one of the most commonly broken indicators in circulation, because fetching higher-timeframe data in Pine Script has a well-known trap. The naive implementation requests the daily high and low with lookahead enabled and no bar offset, which makes historical bars display information (the day's final high and low) that was not knowable until that day ended. The chart then shows perfect-looking levels across history that a live trader could never have seen, and any backtest touching them peeks into the future. The correct implementation requests the prior completed daily bar — offsetting the series by one bar and keeping lookahead off — so the plotted levels on every bar are exactly what was known at that moment. The levels themselves are purely descriptive: they mark where yesterday's trading stopped, nothing about where today's will. This page is educational only, not financial advice, and trading involves risk of loss.

How it works

The mechanics of the correct version are worth spelling out. request.security(syminfo.tickerid, "D", high[1], lookahead = barmerge.lookahead_off) asks the daily timeframe for its high one completed bar back, merged without lookahead. On any intraday bar, this returns the high of the last daily bar that had already closed at that point in time — which is precisely the 'previous day high' a live trader would have known. Contrast the broken version: requesting high (no offset) with barmerge.lookahead_on returns the current day's final high on every intraday bar of that day, including bars printed at 9 a.m. when the day's high had not happened yet. On a live chart both versions look identical for today (the repainting one keeps updating), but on historical bars the broken version silently substitutes hindsight, so its history is a fiction. This is exactly the class of defect a repaint checker exists to catch: the test is whether the value plotted on a historical bar equals the value that was available in real time on that bar. There is one legitimate combination of lookahead_on with a [1] offset that older Pine versions used for the same effect, but in v6 the offset-plus-lookahead_off form is the clear, safe idiom.

How traders read it

• PDH and PDL are fixed for the whole trading day: they mark the extremes of yesterday's completed range and do not move intraday (if they move, the script is wrong).
• Price trading between PDH and PDL means today has so far stayed inside yesterday's range — a factual observation often described as 'inside day' conditions.
• A move beyond PDH or PDL states that today's range has exceeded yesterday's in that direction; many traders watch these levels, which is itself the main reason they matter as shared reference points.
• A poke beyond the level followed by a return inside is frequently labeled a 'failed break' — a description assigned after the fact, not a signal with predictive standing.
• Distance from the current price to PDH/PDL gives a quick sense of where today sits within (or beyond) yesterday's traded range.
• Check what 'day' means on your data: exchange sessions, electronic sessions, and broker server midnight can produce different daily bars and therefore different levels.

Common settings

There is little to configure: the higher timeframe is "D" by convention, though the same pattern generalizes to previous week ("W") or previous month ("M") levels. The meaningful choice is hidden in the data: whether the daily bar comes from the exchange session or a 24-hour electronic session changes the high and low. Some traders also plot the previous day's close or the midpoint of the previous range alongside PDH/PDL. Applicable on any intraday timeframe.

Strengths

• Completely objective and deterministic: yesterday's high and low are matters of record, with zero parameters to curve-fit.
• Widely watched shared reference levels, which gives them practical relevance as coordination points regardless of any theory about them.
• The correct implementation is fully non-repainting, making it safe to use in alerts and historical study.
• An ideal minimal example for learning safe request.security usage — the wrong and right versions differ by a few characters with completely different integrity.
• Works identically across forex, futures, crypto, and equities (subject to session-definition differences).

Pitfalls to watch

• The lookahead trap: the naive request.security call with lookahead_on and no offset paints today's final high/low onto bars printed before those extremes existed — historical bars become fiction and any backtest using them is invalid.
• Even without lookahead, requesting the current daily bar's high (no [1] offset) repaints intraday as the day's range expands; only the prior completed bar is stable.
• Session ambiguity: 'the day' differs between exchange sessions, 24-hour sessions, and broker midnights, so two correct scripts can still disagree about the levels.
• Descriptive, not predictive: PDH/PDL mark where trading stopped yesterday; price breaks through them routinely, and no level implies a reaction.
• Gap opens can leave price far beyond both levels from the first bar of the day, making them irrelevant for that session.
• Alert conditions built on a repainting version will fire at moments that do not correspond to anything reproducible — gate signals on confirmed bars and verify with a repaint check.

Pine v6 example

//@version=6
indicator("Previous Day High/Low", overlay = true)

htf = input.timeframe("D", "Higher Timeframe")

// CORRECT: prior completed HTF bar, lookahead off -> non-repainting
pdh = request.security(syminfo.tickerid, htf, high[1], lookahead = barmerge.lookahead_off)
pdl = request.security(syminfo.tickerid, htf, low[1],  lookahead = barmerge.lookahead_off)

// WRONG (do not use): request.security(..., htf, high, lookahead = barmerge.lookahead_on)
// paints the day's FINAL high onto bars before it existed.

plot(pdh, "Prev Day High", color = color.teal,   style = plot.style_linebr)
plot(pdl, "Prev Day Low",  color = color.maroon, style = plot.style_linebr)

brokeHigh = ta.crossover(close, pdh)  and barstate.isconfirmed
brokeLow  = ta.crossunder(close, pdl) and barstate.isconfirmed
plotshape(brokeHigh, "Above PDH", style = shape.triangleup,   location = location.belowbar, color = color.gray)
plotshape(brokeLow,  "Below PDL", style = shape.triangledown, location = location.abovebar, color = color.gray)

Pro tip: Test any PDH/PDL script the way a repaint checker does: note the plotted level on a live bar, then reload the chart after the day closes and confirm the historical bar still shows the same value. If the level 'improved' after the fact, the script is using future data and its history cannot be trusted for study or backtesting. The levels themselves are just yesterday's facts — useful context, never a forecast. Educational content only, not financial advice; trading involves risk of loss.

Educational only — not financial advice, not a recommendation to trade. No indicator is predictive; trading involves substantial risk of loss.