Source maps can sometimes be tricky to get going. If you’re having trouble, try the following tips.

Verify your source maps are built correctly

We maintain an online validation tool that can be used to test your source (and source maps) against:

Alternatively, if you are using Sentry CLI to upload source maps to Sentry, you can use the –validate command line option to verify your source maps are correct.

Verify sourceMappingURL is present

Some CDNs automatically strip comments from static files, including JavaScript files. This can have the effect of stripping your JavaScript file of its sourceMappingURL directive, because it is considered a comment. For example, CloudFlare has a feature called Auto-Minify which will strip sourceMappingURL if it is enabled.

Double-check that your deployed, final JavaScript files have sourceMappingURL present.

Alternately, instead of sourceMappingURL, you can set a SourceMap HTTP header on your minified file. If this header is present, Sentry will use it to discover the location of your source map.

Verify artifact names match sourceMappingURL

When uploading source maps to Sentry, you must name your source map files with the same name found in sourceMappingURL.

For example, if you have the following in a minified application file, app.min.js:

//-- end app.min.js
//# sourceMappingURL=

Sentry will look for a matching artifact named exactly

Note also that Sentry will resolve relative paths. For example, if you have the following:

// -- end app.min.js (located at

Sentry will resolve sourceMappingURL relative to (the root path from which app.min.js was served). You will again need to name your source map with the full URL:

If you serve the same assets from multiple origins, you can also alternatively use our tilde (~) path prefix to ignore matching against protocol + hostname. In which case, ~/dist/js/, will also work. See: Assets Accessible at Multiple Origins.

Verify artifacts are uploaded before errors occur

Sentry expects that source code and source maps in a given release are uploaded to Sentry before errors occur in that release.

If you upload artifacts after an error is captured by Sentry, Sentry will not go back and retroactively apply any source annotations to those errors. Only new errors triggered after the artifact was uploaded will be affected.

Verify your source maps work locally

If you find that Sentry is not mapping filename, line, or column mappings correctly, you should verify that your source maps are functioning locally. To do so, you can use Node.js coupled with Mozilla’s source-map library.

First, install source-map globally as an npm module:

npm install -g source-map

Then, write a script that reads your source map file and tests a mapping. Here’s an example:

var fs        = require('fs'),
    path      = require('path'),
    sourceMap = require('source-map');

// file output by Webpack, Uglify, etc.
var GENERATED_FILE = path.join('.', '');

// line and column located in your generated file (e.g. source of your error
// from your minified file)
var GENERATED_LINE_AND_COLUMN = {line: 1, column: 1000};

var rawSourceMap = fs.readFileSync(GENERATED_FILE).toString();
var smc = new sourceMap.SourceMapConsumer(rawSourceMap);

var pos = smc.originalPositionFor(GENERATED_LINE_AND_COLUMN);

// should see something like:
// { source: 'original.js', line: 57, column: 9, name: 'myfunc' }

If you have the same (incorrect) results locally as you do via Sentry, double-check your source map generation configuration.

Verify your source files are not too large

For an individual artifact, Sentry accepts a max filesize of 40 MB.

Often users hit this limit because they are transmitting source files at an interim build stage. For example, after Webpack/Browserify has combined all your source files, but before minification has taken place. If possible, send the original source files.

Verify artifacts are not gzipped

The Sentry API currently only works with source maps and source files that are uploaded as plain text (UTF-8 encoded). If the files are uploaded in a compressed format (e.g. gzip), they will be not be interpreted correctly.

This sometimes occurs with build scripts and plugins that produce pre-compressed minified files. For example, Webpack’s compression plugin. You’ll need to disable such plugins and perform the compression after the generated source maps / source files have been uploaded to Sentry.