Open a .fit file — in your browser, without installing anything

Drop the file below. It is read on your device by the same parser we use for everything else, and you will see what is actually in it — device, dates, record types, field counts.

What a .fit file is

FIT — Flexible and Interoperable Data Transfer — is the binary format Garmin created and most of the industry adopted. A file is not a table. It is a stream of messages, each one preceded, somewhere earlier in the file, by a definition that says which fields that message carries and in what order. Nothing in the file is self-describing without its definition.

That design is why a text editor shows you nothing, and why so many converters produce a partial result: they read the first definition for a given slot and cache it. In 52.85% of 68,068 real files the definitions are replaced mid-file — 35,971 files, 566,605 times in total. A parser that caches loses everything after the first replacement, silently.

What you get from this page

• The device. Read from the file's own file_id message, not guessed from the filename.
• The dates it covers. Useful mostly for answering "is this the file I think it is?".
• Every record type present — record, session, lap, monitoring and whatever else your device wrote.
• Every field, with a count. This is the part that tells you whether the data you are looking for is actually in there.

What you do not get is the measurements themselves. This page answers "what is in this file"; it deliberately does not print your heart rate onto a web page, and the summary you can download contains structure and counts only.

Which devices this works with

Any device that writes FIT. Across the corpus we test against, that is 46 distinct manufacturers — bryton, bsx_athletics, cannondale, concept2, coros, cycplus, development, dynastream, garmin, geoid, hammerhead, ifor_powell and more — writing 241 different versions of the format between them.

Of 68,068 real files, 68,064 parse completely and 4 do not.