# Minify inline JavaScript (rewrite_javascript_inline)

Minifies inline JavaScript. The rewrite_javascript_inline filter: what it does, its risks and the Apache, nginx and IIS directives.

Canonical URL: https://modpagespeed.com/docs/filters/rewrite_javascript_inline/

- Category: JavaScript
- CoreFilters: Yes
- OptimizeForBandwidth: Yes
- Risk: Generally safe

`rewrite_javascript_inline` minifies the contents of `<script>` blocks in the HTML itself, in place. No URL changes and nothing new is cached; the smaller script simply rides along inside every page view. Blocks whose `type` does not denote executable JavaScript, such as JSON-LD data islands and HTML templates, are left as they are.

## How it works

The three filters on this section share one minifier. It removes comments and collapses whitespace; identifiers, string literals, regular expressions and property names are emitted unchanged. It keeps a line break wherever automatic semicolon insertion could otherwise merge two statements into one. [How safe JavaScript minification handles automatic semicolon insertion](https://modpagespeed.com/blog/safe-javascript-minification-semicolon-insertion/) has the details.

Inline scripts tend to be short, so the saving per block is small; the filter's job inside the compound is to leave no script unminified. Like the external half, `rewrite_javascript_inline` is in CoreFilters and in OptimizeForBandwidth, and it can be enabled by itself.

`rewrite_javascript_inline` never moves a block or changes when it runs; it only shrinks the text between `<script>` and `</script>`. On pages whose HTML is served many times between deploys that small saving repeats on every serve, which is where the filter earns its place.

## When to use it

- In CoreFilters, the default RewriteLevel: it runs unless you disable it.
- Part of OptimizeForBandwidth, the level that optimizes resources without changing their URLs.
- Also switched on by [`rewrite_javascript`](https://modpagespeed.com/docs/filters/rewrite_javascript/).
- Risk rating on these docs: **Generally safe**.

## Risks

- The minifier never renames identifiers; the historical failure mode is a script that inspects its own source text, for example through `Function.prototype.toString()`, and reacts to the changed formatting.

- Verify with the `X-Mod-Pagespeed` response header and a `?PageSpeedFilters=-rewrite_javascript` comparison; [Is it working?](https://modpagespeed.com/docs/is-it-working/) has the steps.

## Configuration

Enable it in the module configuration, at server, virtual-host or location scope:

**Apache**

```apache
ModPagespeedEnableFilters rewrite_javascript_inline
```

**nginx**

```nginx
pagespeed EnableFilters rewrite_javascript_inline;
```

**IIS (pagespeed.config)**

```text
pagespeed EnableFilters rewrite_javascript_inline
```

It is on by default under CoreFilters; to turn it off:

```text
ModPagespeedDisableFilters rewrite_javascript_inline   # Apache
pagespeed DisableFilters rewrite_javascript_inline;   # nginx
pagespeed DisableFilters rewrite_javascript_inline   # IIS
```

Scoping, `ForbidFilters` and the thresholds filters read: [Choosing filters](https://modpagespeed.com/docs/filter-selection/).

## Frequently asked questions

**What does the rewrite_javascript_inline filter do?**

`rewrite_javascript_inline` minifies the contents of `<script>` blocks in the HTML itself, in place. No URL changes and nothing new is cached; the smaller script simply rides along inside every page view. Blocks whose `type` does not denote executable JavaScript, such as JSON-LD data islands and HTML templates, are left as they are.

**Is rewrite_javascript_inline enabled by default?**

Yes. `rewrite_javascript_inline` is in CoreFilters, the default RewriteLevel, so it runs unless you turn it off with `DisableFilters`. It is also part of the OptimizeForBandwidth level.

**How do I turn off rewrite_javascript_inline?**

Add `ModPagespeedDisableFilters rewrite_javascript_inline` on Apache or `pagespeed DisableFilters rewrite_javascript_inline;` on nginx. On IIS, add `pagespeed DisableFilters rewrite_javascript_inline` to pagespeed.config.

## Related filters

- [`rewrite_javascript`](https://modpagespeed.com/docs/filters/rewrite_javascript/): Minify JavaScript
- [`rewrite_javascript_external`](https://modpagespeed.com/docs/filters/rewrite_javascript_external/): Minify external JavaScript
- [`combine_javascript`](https://modpagespeed.com/docs/filters/combine_javascript/): Combine JavaScript
- [`defer_javascript`](https://modpagespeed.com/docs/filters/defer_javascript/): Defer JavaScript
- [`extend_cache_scripts`](https://modpagespeed.com/docs/filters/extend_cache_scripts/): Extend cache for scripts
- [`include_js_source_maps`](https://modpagespeed.com/docs/filters/include_js_source_maps/): Include JS source maps
- [`inline_javascript`](https://modpagespeed.com/docs/filters/inline_javascript/): Inline JavaScript
- [`make_show_ads_async`](https://modpagespeed.com/docs/filters/make_show_ads_async/): Async AdSense

This page is drawn from the [rewrite_javascript_inline entry on JavaScript filters](https://modpagespeed.com/docs/javascript-filters/#rewrite_javascript_inline). Every filter in one table: [PageSpeed filters](https://modpagespeed.com/docs/filters/).