Prebid.js Guide: Events, Bidder Adapters, Releases and Debugging

Prebid's documentation is large and spread across sections. This map points each common task to the right page.

Two caveats. Prebid's "Important Prebid.js Releases" page stops at version 8.0, so use the per-version release notes and GitHub instead. And the source code is the final word: event names, for example, are defined in src/constants.ts.

Prebid.js emits an event at each step of an auction. Pages and modules subscribe with pbjs.onEvent(eventType, handler, id) and unsubscribe with pbjs.offEvent. Calling pbjs.getEvents() returns a copy of every event since page load, each with eventType, args, id and elapsedTime (onEvent docs; getEvents docs, both accessed 9 November 2026).

Sources: getEvents, onEvent, Prebid's troubleshooting guide for noBid, and constants.ts at 11.47.0. Version 11.0 removed addAdUnits and seatNonBid; listeners on those names now never fire (Prebid.js 11.0 notes).

Register handlers inside pbjs.que so they run once Prebid.js has loaded, and before requestBids, so no event is missed. The property names below, such as timeToRespond, bidderCode and auctionId, are the ones Prebid's own troubleshooting examples use.

Log each bidder's latency and outcome:

Act once on a single ad unit, then stop listening. The id argument limits a bidWon handler to one ad unit code (offEvent docs).

Send render failures to your own endpoint, which Prebid lists as a use for adRenderFailed and auctionDebug. The URL is a placeholder.

For production analytics, prefer an analytics adapter over hand-written listeners. Adapters register through pbjs.enableAnalytics, can sample with options.sampling, and can include or exclude events by name (enableAnalytics docs). Server-side outcomes reach the browser through the pbsAnalytics event; the server half is covered in Prebid Server analytics and debugging.

The Prebid.js bidders page lists every bidder code with its parameters and declared features. Prebid's downloadable data marks 733 entries as client-side adapters, including aliases (bidder-data.csv, last modified 3 November 2026). The repository counts files instead: 535 *BidAdapter files at tag 11.47.0 and 537 on the master branch on 7 November 2026. Some files serve several bidder codes as aliases, so a code you need may live in another company's file; the README tells you to search the repository when that happens (Prebid.js README).

You compile in only the adapters you use. From a clone, after npm ci, run gulp build --modules=openxBidAdapter,rubiconBidAdapter,sovrnBidAdapter, or pass a JSON file with the list. The README also shows npm install prebid.js with ES module imports for teams that bundle Prebid.js into their own build (README).

Save that list as modules.json and build with gulp build --modules=modules.json. Each bidder you add is another network call from the reader's browser. Moving some bidders to Prebid Server trades those calls for user matching, as explained in header bidding vs server-side bidding and Prebid Server cookie sync.

A bid adapter is a module that registers a spec object with registerBidder. Prebid's guide lists the functions the spec provides (bidder adaptor guide, accessed 9 November 2026).

Here is a minimal adapter for an imaginary bidder, written as an ES module. It sends one POST per auction and maps OpenRTB-style bids back.

The rules matter as much as the code. Adapters may not load external code, may not fire network requests or pixels outside buildRequests and getUserSyncs, and may not touch ad slots directly. Each submission needs the adapter file, a markdown file with a maintainer email and test parameters, unit tests, and a docs pull request (bidder adaptor guide). Since 11.0, Prebid prefers TypeScript for new modules (Prebid.js 11.0 notes). For OpenRTB back ends, Prebid's ORTB converter library implements most of buildRequests and interpretResponse for you.

A Prebid.js adapter does not run in Prebid Server. The server needs its own adapter, built in Go first, as described in Prebid Server bidder adapters.

Sources: GitHub releases for dates, Prebid.js 11.0 notes, setConfig user sync docs and the troubleshooting guide, all accessed 9 November 2026.

Upgrading within a major line is usually routine, but read the notes for the adapters you use, because almost every release changes some of them. A major upgrade needs a test plan. Version 11.0 rejects bids whose media type is not in the ad unit, unless you set auctionOptions.rejectInvalidMediaTypes to false. It also makes the storageControl module fail undisclosed storage use instead of warning, and it removes the customSlotMatching argument of setTargetingForGPTAsync (Prebid.js 11.0 notes).

Pin what you ship. In September 2025, GitHub published an advisory that the Prebid.js npm package had been briefly compromised in version 10.9.2, fixed in 10.10.0 (GHSA-jwq7-6j4r-2f92). Build from a locked dependency tree, review version bumps, and host the built file yourself.

Add pbjs_debug=true to the page URL. Prebid.js then stops hiding its JavaScript errors and logs each step, such as "Calling bidder" and "Set key value for placement", to the console (troubleshooting guide). The same effect comes from pbjs.setConfig({ debug: true }). When the page also uses Prebid Server, debug mode makes the server adapter send ext.prebid.debug: true, so the server response carries its own debug data (Prebid Server troubleshooting).

Then work through the console:

1. pbjs.version to confirm the release you think you shipped.
2. pbjs.installedModules to confirm which modules the build contains.
3. pbjs.getConfig() to check timeouts, price granularity, consent and s2sConfig.
4. pbjs.getEvents() to replay the event history, including bidTimeout and bidderError.
5. pbjs.getBidResponses() to see each bid by ad unit, with timeToRespond.
6. pbjs.getAdserverTargeting() to see the key-values sent to the ad server.
7. pbjs.getAllWinningBids() to see which Prebid bids rendered.

To test line items without waiting for real demand, the debugging module can intercept bids and return fixed responses.

This setting persists in the browser's session storage, so turn it off with enabled: false when you finish (debugging module docs). The same module can ask Prebid Server for a stored auction response by ID; Prebid notes that this path currently works only with the Java build of Prebid Server.

1. Registering handlers after requestBids. Early events such as auctionInit are already gone. Use pbjs.que and register first.
2. Listening for removed events. addAdUnits and seatNonBid no longer fire in 11.x; use auctionInit and pbsAnalytics.
3. Treating adRenderSucceeded as an impression. Prebid says it only means the render call raised no error.
4. Shipping the full build. The standard build contains every module. Build with --modules so readers download only what you use.
5. Leaving the debugging module on. Its session-storage setting outlives the page you tested.
6. Expecting user syncs in Safari. Since 11.9 and 11.20, Prebid.js fires no syncs, including Prebid Server's, in Safari or in Firefox and Chrome on iOS.
7. Floating dependency versions. The 10.9.2 incident shows why a lockfile and a reviewed upgrade matter.

1. GitHub, prebid/Prebid.js releases, including 9.0.0 (13 June 2024), 10.0.0 (1 July 2025), 11.0.0 (12 March 2026), 11.7.0, 11.9.0, 11.20.0, 11.29.0, 10.29.2 and 11.47.0 (4 November 2026). https://github.com/prebid/Prebid.js/releases
2. GitHub, prebid/Prebid.js at tag 11.47.0: src/constants.ts, package.json, modules/ (accessed 9 November 2026). https://github.com/prebid/Prebid.js/tree/11.47.0
3. GitHub, prebid/Prebid.js README (master, accessed 9 November 2026). https://github.com/prebid/Prebid.js
4. Prebid.org, "pbjs.onEvent", "pbjs.offEvent", "pbjs.getEvents", "pbjs.enableAnalytics" (accessed 9 November 2026). https://docs.prebid.org/dev-docs/publisher-api-reference/getEvents.html
5. Prebid.org, "How to Add a New Prebid.js Bidder Adapter" (accessed 9 November 2026). https://docs.prebid.org/dev-docs/bidder-adaptor.html
6. Prebid.org, "Prebid.js 11.0 Release Notes and Publisher API Changes" (accessed 9 November 2026). https://docs.prebid.org/dev-docs/pb11-notes.html
7. Prebid.org, "Troubleshooting Prebid.js" (accessed 9 November 2026). https://docs.prebid.org/troubleshooting/troubleshooting-guide.html
8. Prebid.org, "Module: Debugging" (accessed 9 November 2026). https://docs.prebid.org/dev-docs/modules/debugging.html
9. Prebid.org, "pbjs.setConfig: Configure User Syncing" (accessed 9 November 2026). https://docs.prebid.org/dev-docs/publisher-api-reference/setConfig.html
10. Prebid.org, "Prebid.js Bidders" and "bidder-data.csv" (CSV last modified 3 November 2026). https://docs.prebid.org/dev-docs/bidders.html