# Overnight & ETH Levels

Also known as: ONH/ONL, RTH vs ETH.
A Support/Resistance & Levels concept (Anchored/reference levels) in the LuxAlgo Library, with 1 indicator implementation.

## What are Overnight & ETH Levels?

Overnight and ETH levels are reference prices formed outside the regular session: the overnight high and low (ONH/ONL) built during a futures contract's extended electronic hours, and the pre-market high and low in stocks. Splitting the day into regular and extended sessions is its own charting decision (the RTH vs ETH choice); these levels are what the extended session leaves behind. Because overnight trade runs on thinner volume and narrower participation, its extremes are prices set without the full crowd, and the regular-session open routinely revisits and re-judges them.

The split is a product of market structure. CME's Globex platform launched in 1992 and stretched futures trading toward a 24-hour day while the regular session kept its status as the reference auction. The Market Profile tradition descending from J. Peter Steidlmayer's 1980s work at the Chicago Board of Trade formalized the habit of treating regular hours as the session of record and overnight activity as inventory to be resolved, and equities followed once electronic communication networks opened pre-market trading to a broad audience in the late 1990s.

That makes ONH, ONL, and the pre-market extremes the first working map of a trading day: the open either rotates inside the overnight range or breaks an overnight extreme, and what happens at those levels shows whether the early move is being accepted or faded. Stops also collect just beyond the overnight extremes, which is why sweeps of the ONH or ONL are a recurring intraday event.

In practice the overnight session contributes a small family of references: the ONH and ONL, the overnight midpoint, and for stocks the pre-market high and low, all layered onto the same map as [prior period levels](https://www.luxalgo.com/library/concept/prior-period-levels/) such as yesterday's high, low, and settlement, plus the day's [period opens](https://www.luxalgo.com/library/concept/period-opens/). Each is then a candidate [support](https://www.luxalgo.com/library/concept/support-level/) or [resistance level](https://www.luxalgo.com/library/concept/resistance-level/) whose meaning is settled by how price behaves on arrival, the same acceptance-versus-rejection reads covered by [level interaction rules](https://www.luxalgo.com/library/concept/level-interaction-rules/). Confluence upgrades a level: an ONH sitting on yesterday's high or a [floor pivot](https://www.luxalgo.com/library/concept/floor-pivots/) is watched harder than either alone.

## How to mark overnight and ETH levels

The levels take a minute to mark once the session boundaries are set:

1. Turn on extended-hours data, or the overnight session will not exist on the chart: futures need the full ETH feed, stocks the pre-market and after-hours prints.
2. Define the overnight window: for US index futures, conventionally everything between the regular close and the next regular open; for stocks, the pre-market span your platform uses.
3. Mark the highest and lowest prices of that window as the ONH and ONL (or pre-market high and low), and optionally the midpoint between them.
4. Extend the levels across the regular session and watch the first interactions: acceptance beyond an extreme argues for range extension, an immediate reclaim argues for a fade.

## How traders use it

- To frame the open: where the regular session opens relative to the overnight range (inside it, above the ONH, below the ONL) sets the day's first bias, and interaction with the opening range shows whether that bias holds.
- For breakout-or-fade decisions: a push through the ONH that holds is treated as range extension, while a poke through it that immediately returns inside is a classic fade back toward the other side of the overnight range.
- As a liquidity map: resting stops beyond overnight extremes make the ONH and ONL common sweep targets, so liquidity-focused frameworks watch them for stop-runs before the day's more durable move.
- As confluence input: overnight extremes that land on yesterday's high or low, a [Camarilla](https://www.luxalgo.com/library/concept/camarilla/) band, or a [supply or demand zone](https://www.luxalgo.com/library/concept/supply-and-demand-zones/) mark spots where separate methods agree, and those earn priority over lone levels.
- As an inventory read: a night spent trending one way leaves overnight participants positioned one way, and profile-influenced traders watch for the early session to correct that inventory back toward the overnight midpoint before the day's real auction begins.

## Overnight & ETH Levels vs other daily references

- **Prior Period Levels** (https://www.luxalgo.com/library/concept/prior-period-levels/): Yesterday's high, low, and close formed with full regular-session participation; overnight extremes formed on thin trade. Both carry forward, but many traders weight the regular-session set more and treat overnight extremes as newer, less-tested evidence.
- **Period Opens** (https://www.luxalgo.com/library/concept/period-opens/): An open is a single print that starts a period; overnight levels are the extremes a whole session left behind. The daily open usually sits inside the overnight range, and the relationship between the two frames the first hour.
- **Floor Pivots** (https://www.luxalgo.com/library/concept/floor-pivots/): Pivots are computed from yesterday's OHLC by formula, so they exist even where no trade occurred; overnight levels are actual traded extremes. Where a formula level and a traded extreme coincide, the spot earns extra attention.

## FAQ

### What counts as the overnight session?

Convention varies by instrument. For US index futures it is generally everything between the regular-session close and the next regular-session open on the nearly 24-hour electronic market. For stocks it is the pre-market and after-hours prints outside the core exchange session. Platforms differ on exact boundaries, so two traders' overnight highs can differ; what matters is applying one definition consistently.

### Are overnight levels as meaningful as regular-session levels?

They form on lighter volume, so some traders discount them relative to regular-hours extremes. In practice they still produce frequent reactions, partly because so many intraday traders watch the same ONH/ONL and rest stops just beyond them. Treat them as widely observed reference points whose significance is confirmed or denied by how the regular session actually trades around them.

### Do overnight levels apply to stocks or just futures?

Both, under different names. Futures traders speak of the overnight or Globex high and low; equity traders use the pre-market high and low formed in the thinner extended-hours book. The logic is identical: extremes set without full participation get re-tested when the whole crowd arrives at the regular open.

### Why are overnight highs and lows swept so often?

Two reasons work together. Stops from overnight positions and early entries rest just beyond those extremes, making them natural targets, and the prices were set on thin volume, so the regular session frequently probes past them to test whether real interest exists there. A sweep that fails and returns inside the range is itself a common fade setup.

### Should my chart show extended-hours data all the time?

It depends on the method. Level traders usually keep ETH data on so the overnight range stays visible; profile and auction traders often keep a clean RTH chart and mark overnight extremes onto it. A common compromise is two charts, one per convention, since indicator values also change when overnight bars are included.

### How long do overnight levels stay relevant?

Mostly for that trading day; by the next session a fresh overnight range replaces them. An extreme that was never tested can stay live somewhat longer, the way any untouched level does, but most intraday traders reset the map daily and promote only the untested extremes.

## Implementations in the Library

- Overnight & ETH Levels (LuxAlgo): https://www.luxalgo.com/library/indicator/overnight-and-eth-levels/

## Related concepts

- Prior Period Levels: https://www.luxalgo.com/library/concept/prior-period-levels/
- All-time & 52-week Extremes: https://www.luxalgo.com/library/concept/all-time-and-52-week-extremes/
- Monday Range: https://www.luxalgo.com/library/concept/monday-range/
- Anchored VWAP As Level: https://www.luxalgo.com/library/concept/anchored-vwap-as-level/
- Period Opens: https://www.luxalgo.com/library/concept/period-opens/
- Naked POC As Level: https://www.luxalgo.com/library/concept/naked-poc-as-level/
- Max Pain Level: https://www.luxalgo.com/library/concept/max-pain-level/
- Option Strike Walls: https://www.luxalgo.com/library/concept/option-strike-walls/

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Source: https://www.luxalgo.com/library/concept/overnight-and-eth-levels/ (LuxAlgo Library, the encyclopedia of trading & technical analysis). Free to use with attribution: https://www.luxalgo.com/library/license/