KEI, the Keyword Efficiency Index: which keywords are worth it

KEI, the Keyword Efficiency Index, is the number Applyra uses to weigh one keyword's traffic score against its difficulty score. It answers the only question that matters once you have both numbers: does the demand for this term outweigh what it would cost you to rank for it? A KEI of 1.0 means demand and competition are level. Above that, the term gives back more than it asks.

The four KEI tiers

Those tiers are what the Keywords Inspector shows as the opportunity badge on every keyword you look at. KEI is built from the same traffic and difficulty numbers displayed next to it, so the three never disagree on screen.

Why the highest traffic keyword is usually the wrong target

Take two terms. One carries heavy demand and equally heavy competition, so its KEI lands just under 1.0. The other is modest on both counts and comes out above it. The first looks ten times more attractive on a spreadsheet sorted by volume, and it is the one every established app in the category already owns. You will not rank on it, so its real return is zero. The second is a term you can hold a top position on, on a market that is small but real.

That is the whole argument for KEI, and it is why Applyra ranks opportunities by efficiency instead of by raw demand. Our 2026 study puts a figure on the trap: going from one word to three cuts difficulty roughly in half on the App Store and cuts traffic by more than 80%. Long tail is easier to rank for and less often worth ranking for. KEI is what keeps you from walking off either end of that curve.

The bar for an opportunity

An opportunity is more than a good ratio, because a ratio can look healthy on two tiny numbers. So a keyword is only an opportunity when the whole picture holds at once: you are not ranking for it yet, the term carries real demand rather than being a dead niche, the competition is within reach of an app your size, and the ratio is in your favour.

That is a deliberately narrow filter, and it is the point. When none of your candidates clears it, the listing has no easy win left and the work is elsewhere, usually in ASO Health. Where to find the candidates is covered in keyword suggestions.

Where KEI shows up in Applyra

It is not only a research metric. Inside the visibility score, an efficient keyword carries more than an inefficient one. Ranking third on a term nobody searches is worth less than ranking tenth on one that brings real traffic, and the score says so instead of pretending the two are equal.

How to use KEI when you pick keywords

The practical loop is short. Pull candidates from the Keywords Inspector or from a niche analysis, sort by KEI, keep the Good and Excellent ones that are also relevant to what your app actually does, then spend your indexed characters on them in the order the fields carry weight. A high KEI on a term your app has no business ranking for is still a wasted field, and no ratio can tell you that. You can.