sphinx-unified-search

⚠️ Work in progress. This project is under active development. Configuration options and behavior may change without notice. It has not been fully tested for production use, but early testers and feedback are very welcome. Please open an issue if you hit problems or have suggestions.

Cross-project search for Sphinx documentation

sphinx-unified-search is a Sphinx extension that lets you search across multiple Sphinx documentation sites from a single search box. It works by merging remote searchindex.js files into your project's local search index at build time.

The standard Sphinx search UI is preserved: no new search box, no external service, and no per-query cost.

Features

• Works with existing Sphinx themes
• No JavaScript customization required
• No external search service required
• Preserves the standard Sphinx search UI
• Remote search results link directly to their original documentation pages, keeping traffic on the source sites
• Supports any number of remote Sphinx projects
• Supports token-authenticated fetching for private/internal projects

Who might find this useful

• Upstream / downstream content- if your (product and) docs build on top of an upstream project maintained elsewhere, your users can search the upstream or related (Sphinx) docs without leaving your site.
• Multi-product teams - separate Sphinx sites that share an audience, where users shouldn’t have to know which exact site to search. Or products that are part of a larger ecosystem.
• Internal platform teams - private doc sets that (may) need to be searchable alongside public ones without setting up new infrastructure.

How to use the extension

Installing and configuring sphinx-unified-search is straightforward. If you also want to include a private Read the Docs (RTD) project in the unified search results, complete the extra setup below first.

Configure access to private documentation projects

If you want to include a private RTD project in the unified search, you must create an HTTP header token that can be used to download its searchindex.js.

For each private project:

1. Open the project's Read the Docs settings.
2. Go to "Sharing" and "Add share".
3. Select "HTTP header token" for the "Access type", and a suitable expiry date.
4. Select "Allow access to all versions?" if you intend to use searchindex.js for all versions of the docs set. Otherwise, unselect that option and add the versions that will be used by sphinx-unified-search.

Copy the generated token and store it as a secret environment variable in the RTD project that is building the unified search.

For example, if "PROJECT B" wants to the searchindex.js from "PROJECT A" to its search results, generate the HTTP header token in PROJECT A, and add that as an environment variable in PROJECT B (e.g. PROJECTA_DOCS_TOKEN=<generated HTTP header token>).

Install the extension

Add sphinx-unified-search to the requirements.txt file in your Sphinx project:

sphinx-unified-search

Enable the extension

Add sphinx_unified_search to the extensions list in conf.py:

extensions = [
    "sphinx_unified_search",
]

Configure projects to index for unified search

Configure the list of documentation projects whose search indexes should be included in the unified search.

For each project, specify:

• name: A unique identifier for the project. For search results from projects other than the host project, this value is appended to the page title in the search results.
• base_url: The base URL of the documentation, used as the destination when a user clicks a search result.
• searchindex_url: The URL of the project's searchindex.js.

For private projects, also specify:

• auth_token_env: The name of the environment variable containing the RTD HTTP header token.
• auth_scheme: The authorization scheme to use in the HTTP Authorization header. For RTD HTTP header tokens, set this to "Token".

unified_search_projects = [
    # Public project - no auth needed, plain HTTP fetch
    {
        "name": "Landscape",
        "base_url": "https://ubuntu.com/landscape/docs/",
        "searchindex_url": "https://ubuntu.com/landscape/docs/searchindex.js",
    },

    # Private project - token-gated fetch
    {
        "name": "ProjectA",
        "base_url": "https://documentation.ubuntu.com/projecta/",
        "searchindex_url": "https://documentation.ubuntu.com/projecta/searchindex.js",
        "auth_token_env": "PROJECTA_DOCS_TOKEN",
        "auth_scheme": "Token",
    },
]

Build the docs locally

When building the documentation locally, you must set the environment variables referenced by the auth_token_env entries in unified_search_projects.

For example, if your remote project uses this config:

{
    "auth_token_env": "PROJECTA_DOCS_TOKEN",
    ...
}

Export the corresponding token before building:

export PROJECTA_DOCS_TOKEN="<token>"

Repeat this for each private project included in unified_search_projects set.

Once the required environment variables are set, build or serve the documentation as usual with make html or make run.

Filter search results by project

Add project filter chips to the search results page so visitors can narrow the results to one or more projects:

unified_search_project_filter = True

# Optional: label for this project's own results in the filter.
# Defaults to Sphinx's `project` setting.
unified_search_local_project_name = "My Docs"

When the search has finished, a "Filter by project" row appears above the results, with one chip per project that has results and the number of results next to it. Select one or more chips to show only those projects; select "All" (or deselect every chip) to show everything again. The filter only hides rows: results are not removed, and previews are still loaded for all of them. The selection is stored in the URL (?q=term&project=ProjectA), so it survives a reload and can be shared. The filter is off by default, and isn't shown when results come from only one project.

Fetch remote indexes once per live-preview session

By default, every build downloads each remote searchindex.js again. With sphinx-autobuild (make run), that means a fresh download of every remote index on each rebuild, which slows down the edit-preview loop.

Set the following in conf.py to download each remote index only once per sphinx-autobuild session and reuse it for later rebuilds:

unified_search_cache_remote_indexes = True

The cache is scoped to the running sphinx-autobuild process and stored under the Sphinx doctree directory, so it is discarded when you restart the preview. Regular builds (make html, Read the Docs, CI) are unaffected and always fetch fresh indexes. Only successfully parsed downloads are cached, and the cache key covers the index URL and its resolved authentication, so a changed token or header forces a new download. Tokens themselves are never written to disk.

Some things to note

A few behaviors and limitations to be aware of before you publish a unified search, especially if you include private projects.

Private docs: result previews

On the search results page, each result shows a short preview of the matching content, fetched from the remote project’s page. This request is made client-side in the visitor’s browser, so it can’t use the build-time token, and it is subject to the browser’s same-origin policy.

The preview loads only if the remote page is same-origin or allows cross-origin requests via CORS headers. Otherwise, the extension shows a placeholder message instead. The search results and their links work normally in all cases.

Beware of headings

If you add a private project as a remote of a public docs set, page titles and headings from the private project will appear in the public search results, even though the page content itself won't load. Don't include private projects whose titles or headings contain confidential information.

Build the docs in CI (GitHub Actions)

Adding a secret to a repository doesn't automatically expose it to every workflow run. Each job that needs it must reference it explicitly.

This matters most when the docs build runs in a reusable workflow (for example, uses: ./.github/workflows/build-docs.yml). Secrets aren't inherited by the called workflow by default. A build that works locally with an exported token can therefore fail in CI, or silently skip the private index.

To fix this, pass the secret through in the calling workflow:

jobs:
  build-docs:
    uses: ./.github/workflows/build-docs.yml
    secrets:
      PROJECTA_DOCS_TOKEN: ${{ secrets.PROJECTA_DOCS_TOKEN }}
    # or, to pass all secrets: `secrets: inherit`

The reusable workflow must also declare the secret under on.workflow_call.secrets, and the build step should expose it as an environment variable named in auth_token_env.