Will devtools pick it up automatically?

If the minified file's sourceMappingURL comment points at the address, yes — devtools fetch it when they're open.

Does hosting a source map expose my code?

Yes. A source map contains your original source, readable by anyone who fetches it. That's fine for open-source; for proprietary code it's a deliberate choice.

Why is the map bigger than the bundle?

It contains the full original source plus position mappings, so it's routinely larger than the minified output it describes.

Host a source map and serve it from a URL

Put a .map file at a public address so browser devtools can trace minified code back to the original source.

You can host:

Drop your source map here

Any other file works too — up to 25.0 MB, or 100.0 MB for a whole site

Free to use. Your MAP file is live at your-name.99helpers.site in about ten seconds.

What is a .map file?

A source map is a JSON file linking minified production code back to the original source, so a stack trace points at the line you actually wrote rather than at column 4,812 of a single-line bundle. Browsers fetch it only when devtools are open.

What people use MAP files for

Debugging minified production JavaScript
Readable stack traces in error monitoring
Mapping compiled CSS back to Sass or Less
Investigating a bug in a deployed build

What opens a MAP file

Chrome, Firefox and Safari devtools
Sentry and error monitoring services
Every bundler, which generates them
Any browser, which displays the JSON

How to host a MAP file

1
Drop your MAP file in
Drag it onto the box at the top of this page, or click to choose it. Files up to 25 MB are supported, and nothing is uploaded until you publish.
2
Pick an address
Type a name and we'll tell you straight away whether it's free. That becomes the link: bundle-map.99helpers.site
3
Publish and share
Create a free account — that step exists so the file is yours to update, replace or delete — and the link is live within seconds.

The same three steps work for any file — see how file hosting works on 99helpers.com.

What happens when someone opens the link

The browser displays the JSON. Devtools fetch it automatically when the bundle's sourceMappingURL comment points at the address.

Why host a MAP file instead of emailing it?

Sometimes you need a source map at a URL for debugging a build without deploying it — hosting one is faster than a full deploy cycle.

Worth knowing before you publish

Source maps expose your original source code to anyone who fetches them; that's fine for open-source and a decision worth making for anything else.
The bundle's sourceMappingURL comment has to point at the address for devtools to find it.
Maps are often larger than the bundle they describe — check the 25 MB limit.

MAP hosting questions

Will devtools pick it up automatically?: If the minified file's sourceMappingURL comment points at the address, yes — devtools fetch it when they're open.
Does hosting a source map expose my code?: Yes. A source map contains your original source, readable by anyone who fetches it. That's fine for open-source; for proprietary code it's a deliberate choice.
Why is the map bigger than the bundle?: It contains the full original source plus position mappings, so it's routinely larger than the minified output it describes.

Put your MAP file online now

It takes about ten seconds, and you only make an account once the file is ready to go live.

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Hosting guides for related formats

Host a JavaScript file Host a JSON file Host a TypeScript file Host a CSS stylesheet Host a Sass (SCSS) file

MAP is one of over 211 formats you can host — see free file hosting for any file type for the full list, or read the hosting guides for other file types.