This addresses #1955
CPU throttling needs to be applied to both the primary puppeteer session
and the secondary CDP session from the DevTools universe to have an
effect.
For network throttling this does not seem to be the case, I can see a
slowdown with the current implementation which only applies the network
throttling to the primary CDP session.
I also had to increase the navigation timeout to prevent timeout errors.
## Summary
Extend the existing `emulate` tool with an `extraHTTPHeaders` parameter
that calls Puppeteer's `page.setExtraHTTPHeaders()` (which uses CDP
`Network.setExtraHTTPHeaders` under the hood).
Closes#1175
## Approach
Per [feedback from
@natorion](https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/1175#issuecomment-4097587153),
this integrates into the existing `emulate` tool rather than adding a
standalone tool. The `emulate` tool is already the central hub for
page-level state modifications (userAgent, viewport, networkConditions,
geolocation, colorScheme), and custom HTTP headers fit naturally
alongside them. This also avoids increasing the MCP tool count and LLM
token overhead.
## Changes
- **`src/types.ts`** — Added `extraHTTPHeaders?: Record<string, string>`
to `EmulationSettings`
- **`src/tools/emulation.ts`** — Added `extraHTTPHeaders` as an optional
zod parameter on the `emulate` tool
- **`src/McpContext.ts`** — Added handler logic in the `emulate()`
method:
- Calls `page.setExtraHTTPHeaders()` when `extraHTTPHeaders` is provided
- Clears from settings when an empty `{}` is passed
- Preserves existing headers when the param is **omitted** (unlike other
emulation settings that reset when omitted) — prevents
`emulate({colorScheme: "dark"})` from accidentally clearing
previously-set headers
- **`tests/tools/emulation.test.ts`** — Added 5 test cases:
1. Sets extra headers on requests
2. Clears headers with `{}`
3. Headers persist across navigations
4. Does not affect other emulation settings
5. Reports correctly per-page (new page has no headers)
## Use Case
This enables setting custom HTTP headers on **all** requests — including
the initial document navigation and `<script>` tag loads — which
`initScript` cannot do since it runs after the document is already
fetched.
## Usage
```js
// Set headers
emulate({ extraHTTPHeaders: { "X-Custom": "value", "Authorization": "Bearer token" } })
// Clear headers
emulate({ extraHTTPHeaders: {} })
// Combine with other emulation settings
emulate({ extraHTTPHeaders: { "X-Branch": "feature-1" }, userAgent: "MyBot/1.0" })
```
---------
Co-authored-by: Alex Rudenko <alexrudenko@chromium.org>
Co-authored-by: Nicholas Roscino <nroscino@google.com>
- add a message about successful configuration
- add a message about the currently emulated geolocation
- switch to comma separate format instead of `x` separator.
Tested with https://www.audero.it/demo/geolocation-api-demo.html
- reduces the token usage.
- makes emulation and script compatible with CLI.
- documents .nullable() and .object() restrictions for the future.
- the emulation tools do not have nullable anymore and undefined would
clear the emulation instead. The model is thus required to provide all
emulation settings at once.
Closes https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/918
- renamed getSelectedPage to getSelectedPptrPage
- removes getSelectedPptrPage from tool interfaces
- moves dialog handling to McpPage
- makes responses to be optionally McpPage-scoped
I split this PR off from my "create one DevTools universe per page" PR
in preparation. This allows tests to re-use browser instances without
creating an `McpContext`.
Drive-by: Move mocked browser/page into utils.ts.
This PR prevents license notices being dropped when creating package for
publication.
This can happen when first import in the file is type-only import that
gets removed during build. When there is no empty line between the
license block comment and such import, the comment is treated as related
to the import and gets removed alongside it.
Adding an empty line between copyright notice and the import fixes the
issue.
Co-authored-by: Piotr Paulski <piotrpaulski@chromium.org>
https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/320
Issue:
It would be very useful to have the ability to simulate offline network
conditions directly through the MCP emulate_network command, similar to
how it's possible in DevTools.
Currently, the command doesn’t support an Offline state, which limits
testing for PWA and offline-first web applications. Adding this option
would make it easier to automate and validate offline behavior through
MCP scripts or tools that rely on this API.
Solution
- Add 'Offline' option to throttlingOptions for simulating offline
network conditions
- Update emulate_network tool to handle offline mode with proper network
conditions
- Update documentation to include offline option and usage instructions
- Add test coverage for offline network emulation functionality
- Enable testing of PWA and offline-first web applications through MCP
Alex Rudenko