FIT Parser - v6.2.7

Parse and encode FIT files in JavaScript and TypeScript, with ESM and CommonJS builds. The API reference follows the package exports; the decoded field reference describes nested values returned through ParsedFit.

Start here

npm install fit-file-parser
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Node.js examples require Node 20 or newer. Follow Parse FIT files for a runnable Node example, browser file input and CommonJS imports.

The narrow entry points keep unrelated decoder/profile code out of that import. Named helpers are also available from the package root.

Guides

• Parse FIT files: inputs, async and callback APIs, concatenated files and output modes.
• Configure parsing: units, CRC checks, structural validation and compatibility behavior.
• Handle errors: validation errors, decoder exceptions and record diagnostics.
• Read raw and developer data: unmapped fields, selected messages and the strict raw reader.
• Encode FIT files: definitions, raw values, timestamps and CRCs.
• Understand decoded fields: optional values, dates, enums and profile lookups.

API and field reference

• FitParser: the default package export, including parseAsync(), parseFilesAsync() and parse().
• FitParserOptions: options for the semantic parser.
• ParsedFit: decoded output and its optional message collections.
• FitEncoder: the encoder, also available from fit-file-parser/encoder.
• readFitMessages: the strict reader, also available from fit-file-parser/raw, with readFitUnsignedField and fitTimestampToUnixMilliseconds for interpreting selected raw fields.
• getFitManufacturerName: profile lookup helpers, also available from fit-file-parser/profile.

The decoded field reference includes nested interfaces and enum types for navigation. These names are not all named package exports. Use ParsedFit and indexed access types as shown in Understand decoded fields; do not import internal source paths.

Documentation is built from the repository source. See the GitHub repository and npm package for releases.