If you searched something like "best way to tag my DJ library", here is the map. There are four tools that will read key and BPM from your audio, plus the oldest method of all, and each one fits a different kind of DJ. None of them is wrong. This page lays out what each costs today, what each actually covers, and where each runs, so you can pick once and move on.
Why do two tools give the same track two different keys?
Because key and BPM are not stored facts inside the file; they are estimates, computed from the audio by an algorithm, and different algorithms disagree at the edges. Tracks that modulate, sit between keys, or lean on vocals and pads confuse key estimators; long intros and syncopation push BPM detectors into double or half time. That is why the practical rule is consistency: one engine for the whole library beats three engines arguing. The full argument is in our guide to accurate key and BPM.
The five ways, side by side
| Way | What it costs | What it covers | Where it runs |
|---|---|---|---|
| Rekordbox analysis | Track analysis is on the Free plan; paid plans reach up to $30 a month for cloud and creative features (rekordbox.com, checked July 2026) | Key and BPM on files you already have, inside your rekordbox library; the natural choice if you play CDJs and export USBs | macOS, Windows |
| Serato analysis | Serato DJ Lite is free; Serato DJ Pro is $11.99 a month or $299 once (serato.com, checked July 2026) | Key and BPM analyzed on import, on files you already have, inside Serato | macOS, Windows |
| Mixed In Key | $58 list (mixedinkey.com, checked July 2026; they run sales) | Key, BPM and energy read from the audio, plus cue points; the respected specialist for the analysis step, results written where DJ software reads them | macOS, Windows |
| Cratefox | $39.99 once, no subscription | Starts one step earlier: finds and downloads tracks from a pasted playlist over your own connection, then tags, sorts and exports a Rekordbox-ready crate | macOS, Windows |
| Manual tagging | Free, paid in evenings | Your ears against a keyboard: as accurate as you are, and the slowest way; also the final check every other row quietly relies on | Anywhere |
Which way fits which DJ?
You play CDJs and your library already exists: let rekordbox analyze everything on import and make it your single source of truth. You live in Serato: same logic, Serato's own analysis, one engine, no mixing of engines. You want a dedicated second opinion with energy levels and cue points: Mixed In Key is the specialist and wears the reputation honestly. Your problem starts before the files exist, as in "I have a playlist, not a library": Cratefox is built for exactly that gap, and tagging is one of the five jobs it does on the way to a finished crate. You trust nothing but your ears: manual tagging still works, and even if you never tag by hand, ear-checking suspect transitions is the habit that catches what every algorithm misses.
Whatever engine you choose, hold it to a number if you can. Ours is published: on the 596 GiantSteps tracks that carry independent expert key labels, Cratefox keys read 75.8% Camelot-exact and 86.4% safe to mix, weak genres listed, misses counted, reproducible from any install. The method and the fine print are on the accuracy page. We have not measured the other tools on that benchmark, so this page makes no accuracy claim about them.
Does the file format change the tags?
Not the estimates themselves, but it changes where they can live: WAV tag support is patchy across players, while MP3 and FLAC carry key and BPM tags cleanly. If you are choosing formats at download time anyway, the plain-science comparison is at MP3 320 vs FLAC vs WAV.
The rule that outlasts the tool choice
One engine, one naming convention, and an ear-check on anything suspicious. A library where every track was tagged by the same engine in the same format, like Artist - Title (Version) with key and BPM in the tags, is readable at a glance in any booth. That habit matters more than which row of the table you picked.