.BR file extension
To open .BR files on Windows, if the file is part of a website (e.g., "app.js.br"), rename/copy it only if needed and plan to decompress it (it is not meant to be opened directly).
To open a .br file, you typically decompress it with a Brotli-capable tool (for example, the official Brotli command-line utilities) and then open the resulting file in its normal app. On the web, .br usually indicates Brotli compression used with HTTP Content-Encoding: br.
Last updated: June 12, 2026
Open on your device
Choose your operating system for a dedicated step-by-step opening guide.
How to open .BR files
Use these platform-specific instructions to open .BR files safely.
Windows
- If the file is part of a website (e.g., "app.js.br"), rename/copy it only if needed and plan to decompress it (it is not meant to be opened directly).
- Install and use a Brotli-capable tool (for example, the Google Brotli command-line utilities from the brotli project) to decompress the .br into the original file.
- Open the decompressed output (such as .js, .css, .html, or .wasm) with the appropriate editor or viewer.
Mac
- If the .br appears as a web asset (like .css.br), treat it as compressed data that must be decompressed first.
- Use a Brotli-capable decompressor (for example, the Google Brotli command-line utilities) to decode the .br file to its original form.
- Open the resulting file in the app that matches its real type (text editor for .js/.css, etc.).
Linux
- Decompress the file using Brotli tooling (the reference brotli utilities are commonly used) to produce the original uncompressed file.
- Open the decompressed output using the appropriate program (e.g., a text editor for .js/.css/.html).
iOS
- There is no common native workflow for directly opening .br as a user file; decompress it on a desktop with Brotli tools, then transfer and open the extracted original file on iOS.
Android
- Android typically won’t open .br directly as a document; decompress it on a desktop with Brotli tools and then open the extracted file on Android.
Security notes
- .br is compressed data; decompressing untrusted .br files can consume significant CPU/memory (a common risk with compressed inputs), so be cautious with very large or unexpected files.
- Treat decompressed output according to its real type: a .br may contain JavaScript, HTML, or other content that could be unsafe to execute if you weren’t expecting it.
- When used on websites, Brotli is an HTTP content coding ("br"); server misconfiguration can accidentally expose pre-compressed assets or cause clients to handle data incorrectly, so validate headers and content handling.
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Can't open this file?
These are the most common causes and fixes when .BR files fail to open.
Common reasons
- Decompression produces an unknown or extensionless file
- The file won’t open in a browser or editor
- Website serves a .br file as a download instead of loading normally
Fix steps
- Look at the original context or name (e.g., "style.css.br" should decompress to "style.css").
- After decompressing, add the correct extension based on what the file is (CSS/JS/HTML/WASM are common for web assets).
OS-specific troubleshooting
What is a .BR file?
A .br file usually stores a Brotli-compressed bitstream defined by RFC 7932. In practice it is often a pre-compressed web asset (such as .js.br or .css.br) meant to be served with HTTP content coding token "br" (Brotli). The file itself is not a document format; it is compressed data that must be decompressed to recover the original content.
Background
Brotli is a general-purpose lossless compression format that is widely used for compressing web resources. In HTTP, it is identified by the content-coding token "br" and commonly sent via the Content-Encoding: br header, as registered by IANA.
Because Brotli is used heavily for web delivery, many .br files you encounter are not intended for manual opening. They are often generated during a build/deploy step (for example, producing pre-compressed versions of CSS/JS) so servers can quickly serve compressed responses to compatible browsers.
The Brotli compressed data format is standardized in RFC 7932, and Google provides a reference implementation and command-line tools that can compress and decompress Brotli streams. Practical guides also commonly treat .br as a Brotli-compressed file that can be decompressed with Brotli utilities or compatible archive tools.
Further reading
Authoritative resources for more details on the .BR format.
Common .BR issues
Decompression produces an unknown or extensionless file
A .br file is just compressed data; it may not include the original filename or extension, especially when it was created for web serving (e.g., "main.js.br" implies the output should be "main.js").
- Look at the original context or name (e.g., "style.css.br" should decompress to "style.css").
- After decompressing, add the correct extension based on what the file is (CSS/JS/HTML/WASM are common for web assets).
The file won’t open in a browser or editor
Trying to open the compressed .br directly will show garbled data because it must be decompressed first.
- Decompress the .br with a Brotli-capable tool (such as the official brotli utilities).
- Open the decompressed output with the appropriate program (text editor for source files, etc.).
Website serves a .br file as a download instead of loading normally
On the web, Brotli is meant to be delivered using HTTP content coding (Content-Encoding: br). If a server is misconfigured, it may serve the pre-compressed file as if it were the actual resource or omit the correct headers.
- If you manage the site, ensure Brotli is delivered as HTTP content coding "br" (Content-Encoding: br) rather than exposing the .br file directly.
- Verify the server sets appropriate headers and serves the original resource URL while using Brotli encoding for transport.
FAQ
Is .br a document format?
No. It usually means the file’s contents are Brotli-compressed data; you must decompress it to get the original file (often a web asset like .js or .css).
What does "br" mean in HTTP?
"br" is the registered HTTP content-coding token for Brotli. Servers can send responses compressed with Brotli using Content-Encoding: br.
Why do I see files like app.js.br or style.css.br?
Those are commonly pre-compressed versions of JavaScript or CSS meant to be served by a web server using Brotli compression for faster delivery. They are usually not intended for manual opening without decompression.
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