My .fit file only shows part of my ride — why, and how to recover it
If a converter shows the start of your ride and then nothing, the file is almost certainly fine — the reader gave up at a point the format expected it to keep going.
Open your file
Drop your file here
a .fit file from a watch or bike computer
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The file redefines itself mid-stream
FIT describes each message with a definition that says which fields follow and in what order, keyed to a small “local type” number. The catch is that a device may reuse a local type later in the same file with a new definition — a different set of fields. A parser that reads the first definition for a slot and caches it forever then decodes every later message with the wrong layout, and usually bails or produces garbage from that point. The correct behaviour is to re-read the definition each time it appears.
How common this is
This is not a rare edge case. Across the corpus this reader is tested against, redefinition happens in a majority of files — the exact share is measured and shown below — so a tool that gets it wrong fails on more files than it succeeds on, just not always visibly. That is why “my ride is cut off” is one of the most common FIT complaints and almost never means the file is damaged.
Read all of it here
Drop the file and this page reads it on your device with a parser that re-reads every definition, so the whole activity comes through — and it tells you how many records it recovered, so you can compare against the partial result your other tool gave you. Nothing is uploaded.
Measured across 68,068 real files: 52.85% of them (35,971 files) redefine a local type at least once, and the most a correct reader recovered from a single otherwise-failing file was 143,973 records.
If this was not your problem, the four things that actually break a .fit file covers the rest, and the file reader opens any file whatever is wrong with it.