EMA Crossover
A fast exponential moving average crossing a slow one, read as a trend change. EMAs weight recent prices more heavily than an SMA.
Also called: exponential moving average · EMA 20 50 · golden cross · death cross
What it means
An exponential moving average applies a decaying weight to older prices, so it turns faster than a simple moving average of the same length. A fast EMA crossing above a slow one is read as a shift to an uptrend, and the reverse as a shift down.
Crossovers are late by construction, and in a range they are worse than late — they whipsaw, firing in both directions with no follow-through. The alignment of the EMAs is generally more informative than the crossing event itself.
The seeding of the first value and the exact smoothing constant both change the printed series, which is why two platforms can show visibly different "20 EMA" lines on the same data.
How OptionLab Pro’s engine uses it
In the live engine
We implement the EMA as an IIR filter with b=[k], a=[1.0, k−1.0] where k = 2/(period+1), seeded on the first array element. That is stated precisely because it is checked: a parity harness compares the Go and Python implementations against a shared fixture to 1e-6 on every CI run, so the two cannot drift. EMA alignment also feeds the regime classifier as an alignment fraction.
go/internal/engine/indicators.go (EMA IIR filter) · go/cmd/parity-checkThe common mistake
Where traders get this wrong
Trading crossovers without a regime filter. In a ranging market the crossover signal is close to noise, and this is the single most common way a backtest that looked fine on trending data fails in a chop. Pair it with a trend-strength measure or expect the whipsaws.
Go deeper
There is a full lesson on this in the Academy, with an interactive widget and a Hindi translation.
Related terms
Educational and analytical content only. OptionLab Pro is not a SEBI-registered investment adviser or research analyst and does not give buy or sell recommendations. Derivatives trading carries a high risk of loss.