Bili Pilot

English | Simplified Chinese

Bili Pilot is an experimental Chrome and Firefox extension that helps stabilize high-bitrate Bilibili playback. It compares the signed CDN routes Bilibili already provides, supports manual route selection, and can pre-cache upcoming DASH segments from the best available route for each segment.

Bili Pilot is an independent community project. It is not affiliated with or endorsed by Bilibili.

Preview

This launch image uses a Retina capture from a real 4K HDR playback test. It shows Bili Pilot comparing Bilibili-provided CDN routes and caching future DASH segments beyond the player's existing buffer.

Install

Bili Pilot works on desktop Chrome 111+ and Firefox 140+ for macOS, Windows, and Linux. Safari, mobile browsers, and browser extension stores are not supported yet.

Chrome: from a release package

1. Download the latest Bili-Pilot-Chrome-x.y.z.zip from the repository's Releases page.
2. Extract the ZIP file. Do not select the ZIP itself in Chrome.
3. Open chrome://extensions.
4. Enable Developer mode in the top-right corner.
5. Select Load unpacked.
6. Select the extracted bili-pilot folder containing manifest.json.
7. Open or reload a Bilibili video page.

Chrome may show a developer-mode warning after restart because this is not a Chrome Web Store installation. The extension must be reloaded from chrome://extensions after updating its files.

Chrome: from source

Use GitHub's Code → Download ZIP action or clone the repository, then load the repository folder containing manifest.json with the same steps above.

There is no build step and no runtime dependency. npm install is not required to use the extension.

Firefox: from a signed release

1. Download Bili-Pilot-Firefox-x.y.z.xpi from the repository's Releases page.
2. Open the downloaded XPI in Firefox and approve the installation.
3. Open or reload a Bilibili video page.

The Firefox artifact is signed by Mozilla. The Chrome ZIP is not a Firefox installer.

Firefox: temporary source install

Developers can also test the same source build as a temporary extension:

1. Download or clone the repository.
2. Open about:debugging#/runtime/this-firefox in Firefox 140 or newer.
3. Select Load Temporary Add-on.
4. Select the repository's manifest.json.
5. Open or reload a Bilibili video page.

Firefox removes temporary extensions when the browser exits. A normal persistent Firefox installation requires an XPI signed by Mozilla.

Quick start

1. Open a regular https://www.bilibili.com/video/... page and start playback.
2. Select a fixed quality such as 1080P60 or 4K so measurements stay on one video representation.
3. Expand the Bili Pilot panel and wait for the active quality and CDN candidates to appear.
4. Run Quick scan to compare route stability.
5. Either select Use to pin a CDN manually, or enable Automatic routing + pre-cache.
6. When pre-cache is enabled, let the player build at least 15 seconds of buffer. The panel will show upcoming segments as Planned, Downloading, Retrying, Ready, or Re-probing.

Ready means the complete byte range is in memory and can be delivered to the player. A partial download is never marked ready and is never served as a cache hit.

Features

• Manual CDN selection: pin any signed route supplied for the active video track.
• Quick and deep scans: compare conservative floor throughput and failures rather than trusting one peak measurement.
• PCDN/MCDN-aware ordering: ordinary official routes are preferred automatically; risk-classified routes remain available for manual choice and last-resort fallback.
• Per-segment route selection: different upcoming segments can be downloaded from different CDNs.
• Adaptive pre-cache: prepare the next 3–8 real DASH segments according to current buffer headroom.
• Player-first scheduling: safe buffered headroom admits one low-priority background transfer; dropping below 15 seconds cancels it. Pausing playback does not discard existing headroom.
• Fail-open delivery: cached bytes are returned only for complete Range coverage; every uncertain case uses Bilibili's original request.
• Local and private: no account service, remote backend, analytics, or telemetry.
• Localized UI: English, Simplified Chinese, and Traditional Chinese follow the browser's UI language automatically.

How it works

A general speed test does not measure the path to the CDN serving a particular Bilibili media file. Bilibili may provide multiple signed URLs for one DASH track, and route quality can vary with time and byte position.

Bili Pilot therefore operates on the real active track:

1. Observe Bilibili playurl data and actual media requests to identify the active representation.
2. Preserve every complete signed candidate URL; never fabricate a route by replacing only the hostname.
3. Compare ordinary candidates first. PCDN/MCDN candidates are used automatically only as last-resort recovery.
4. Parse the DASH sidx, probe future real segments at low priority, and download each complete segment from its best successful route.
5. Return an exact HTTP 206 response only when cached data covers every requested byte; otherwise pass through unchanged.

flowchart LR
  A["Active Bilibili DASH track"] --> B["Signed CDN candidates"]
  B --> C["Manual route selection"]
  B --> D["Low-priority future-segment probes"]
  D --> E["Best route for each segment"]
  E --> F["Bounded complete-segment cache"]
  F -->|"Complete Range"| G["Exact HTTP 206"]
  F -->|"Partial or uncertain"| H["Original player request"]

For the full reasoning and observed failure model, read Problem and solution. For code boundaries and state ownership, read Architecture.

Privacy and permissions

Bili Pilot requests only:

• storage, for the pre-cache preference and non-sensitive local UI state;
• access to Bilibili pages and known media CDN families used by signed video URLs.

Signed URLs are used only for local Range requests. Bili Pilot does not collect or upload browsing history, cookies, page text, account information, signed media URLs, or playback analytics. It has no background service worker or remote configuration service.

Troubleshooting

The panel does not appear

Confirm that the extension is enabled, reload it on chrome://extensions, then reload the Bilibili tab.

The panel keeps waiting for a video

Start playback and wait for a media request. Bili Pilot waits for evidence of the active track instead of guessing from inactive playurl representations.

No CDN candidates appear

The page may not have exposed a supported DASH playurl yet. Try a regular video page and start playback.

Every scan times out

All signed routes may be slow or unavailable on the current network. Bili Pilot cannot invent another authorized CDN.

Pre-cache does not start

Check that pre-cache is enabled, at least 15 seconds are buffered, and the active track exposes a readable SegmentBase.indexRange and sidx. Playback may be paused; pre-cache is driven by safe buffered headroom rather than the play/pause state.

A reachable CDN still stalls

A large Range can transfer most bytes quickly and then stop near its tail. The player can hit its deadline even if that URL eventually returns HTTP 206. A successful small probe is useful evidence, not a guarantee that a later full segment will finish on time.

Limitations

• Bili Pilot can use only the signed candidates returned for the active track. It does not discover arbitrary CDN nodes, bypass account or quality restrictions, or replace a VPN.
• Exact pre-cache requires a readable DASH sidx; manual route selection can still work without one.
• Pre-cache is preventive. It cannot guarantee recovery from cold start, seek, or an already empty buffer.
• Live routing depends on Bilibili continuing to load DASH media through page-visible Fetch/XHR.
• Automated tests verify the mechanics, but real benefit should be evaluated with controlled baseline-versus-enabled playback runs on the same video, quality, interval, and network.

Development

The extension source is plain JavaScript and has no production dependencies. Node.js 18 or newer is needed only for tests.

npm test
npm run check

The suite covers active-track selection, signed routing, PCDN/MCDN classification, Range and sidx parsing, probe failure control, player-first scheduling, multi-CDN retry, cache assembly, protocol parity, stable UI rendering, locales, and the Manifest surface.

When editing extension files, reload the extension on chrome://extensions and then reload the Bilibili tab so both execution worlds receive the new code.

Contributing

Issues and focused pull requests are welcome. Please include:

• the video quality and whether the page is a regular video, multi-part video, or collection;
• the candidate hostnames, with signed query values removed;
• the exact UI or network symptom and reproduction steps;
• baseline-versus-enabled evidence for performance claims;
• passing npm test and npm run check results for code changes.

Do not post complete signed media URLs, cookies, account identifiers, or private browsing data.

Project documentation

• Problem and solution: observed playback failure model, design rationale, and evidence standard
• Architecture: modules, dependency direction, state ownership, and safety invariants
• Releasing: reproducible package, checksum, tag, and first-release workflow

License

MIT © Bili Pilot contributors