Source Maps

Sentry supports un-minifying JavaScript via Source Maps. This lets you view source code context obtained from stack traces in their original untransformed form, which is particularly useful for debugging minified code (e.g. UglifyJS), or transpiled code from a higher-level language (e.g. TypeScript, ES6).

Specify the release

If you are uploading source map artifacts yourself, you must specify the release in your SDK see: Releases. Sentry will use the release name to associate digested event data with the files you’ve uploaded via the releases API, sentry-cli or sentry-webpack-plugin. This step is optional if you are hosting source maps on the remote server.

Generating a Source Map

Most modern JavaScript transpilers support source maps. Below are instructions for some common tools.

UglifyJS

UglifyJS is a popular tool for minifying your source code for production. It can dramatically reduce the size of your files by eliminating whitespace, rewriting variable names, removing dead code branches, and more.

If you are using UglifyJS to minify your source code, the following command will additionally generate a source map that maps the minified code back to the original source:

uglifyjs app.js \
  -o app.min.js.map \
  --source-map url=app.min.js.map,includeSources

Webpack

Webpack is a powerful build tool that resolves and bundles your JavaScript modules into files fit for running in the browser. It also supports various loaders to transpile higher-level languages, reference stylesheets, or include static assets.

We have created a convenient webpack plugin that configures source maps and uploads them to Sentry during the build. This is the recommended way for uploading sources to Sentry. First, install the plugin via:

$ npm install --save-dev @sentry/webpack-plugin
$ yarn add --dev @sentry/webpack-plugin

To allow the plugin to upload source maps automatically, create a .sentryclirc or configure environment variables as described in the CLI configuration docs. Then, add the plugin to your webpack.config.js:

const SentryWebpackPlugin = require('@sentry/webpack-plugin');

module.exports = {
  // other configuration
  plugins: [
    new SentryWebpackPlugin({
      include: '.',
      ignoreFile: '.sentrycliignore',
      ignore: ['node_modules', 'webpack.config.js'],
      configFile: 'sentry.properties'
    })
  ]
};

Alternatively, if you prefer to upload source maps manually, Webpack just needs to be configured to output source maps:

module.exports = {
    output: {
      path: path.join(__dirname, 'dist'),
      filename: "[name].js",
      sourceMapFilename: "[name].js.map"
    }
    // other configuration
};

SystemJS

SystemJS is the default module loader for Angular 2 projects. The SystemJS build tool can be used to bundle, transpile, and minify source code for use in production environments, and can be configured to output source maps.

builder.bundle('src/app.js', 'dist/app.min.js', {
    minify: true,
    sourceMaps: true,
    sourceMapContents: true
});

TypeScript

The TypeScript compiler can output source maps. Configure the sourceRoot property to / to strip the build path prefix from generated source code references. This allows Sentry to match source files relative to your source root folder:

{
    "compilerOptions": {
        "sourceMap": true,
        "inlineSources": true,
        "sourceRoot": "/"
    }
}

Making Source Maps Available to Sentry

Source maps can be either:

  1. Served publicly over HTTP alongside your source files.
  2. Uploaded directly to Sentry (recommended).

Hosting Source Map Files

By default, Sentry will look for source map directives in your compiled JavaScript files, which are located on the last line and have the following format:

//# sourceMappingURL=<url>

When Sentry encounters such a directive, it will resolve the source map URL relative the source file in which it is found, and attempt an HTTP request to fetch it.

So for example if you have a minified JavaScript file located at http://example.org/js/app.min.js. And in that file, on the last line, the following directive is found:

//# sourceMappingURL=app.js.map

Sentry will attempt to fetch app.js.map from http://example.org/js/app.js.map.

Alternatively, during source map generation you can specify a fully qualified URL where your source maps are located:

//# sourceMappingURL=http://example.org/js/app.js.map

While making source maps available to Sentry from your servers is the easiest integration, it is not always advisable:

  • Sentry may not always be able to reach your servers.
  • If you do not specify versions in your asset URLs, there may be a version mismatch
  • The additional latency may mean that source mappings are not available for all errors.

For these reasons, it is recommended to upload source maps to Sentry beforehand (see below).

Uploading Source Maps to Sentry

Except for webpack, the recommended way to upload source maps is using Sentry CLI. If you have used Sentry Wizard to set up your project, it has already created all necessary configuration to upload source maps. Otherwise, follow the CLI configuration docs to set up your project.

Sentry uses Releases to match the correct source maps to your events. To create a new release, run the following command (e.g. during publishing):

$ sentry-cli releases new <release_name>

Note the release name must be unique within your organization and match the release option in your SDK initialization code. Then, use the upload-sourcemaps command to scan a folder for source maps, process them and upload them to Sentry:

$ sentry-cli releases files <release_name> upload-sourcemaps /path/to/files

This command will upload all files ending in .js and .map to the specified release. If you wish to change these extensions – e.g. to upload typescript sources – use the --ext option:

$ sentry-cli releases files <release_name> upload-sourcemaps --ext ts --ext map /path/to/files

Until now, the release is in a draft state (“unreleased”). Once all source maps have been uploaded and your app has been published successfully, finalize the release with the following command:

$ sentry-cli releases finalize <release_name>

For convenience, you can alternatively pass the --finalize flag to the new command which will immediately finalize the release.

Note: You dont have to upload the source files (ref’d by source maps), but without them the grouping algorithm will not be as strong, and the UI will not show any contextual source.

Additional information can be found in the Releases API documentation.

Troubleshooting

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: sourcemaps.io.

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.

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=https://example.com/dist/js/app.min.js.map

Sentry will look for a matching artifact named exactly https://example.com/dist/js/app.min.js.map.

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

// -- end app.min.js (located at https://example.com/dist/js/app.min.js)
//# sourceMappingURL=app.min.js.map

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

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/app.min.js.map, 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('.', 'app.min.js.map');

// 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' }
console.log(pos);

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.