User ID Modules

The three Prebid user ID modules active on every Advlume impression — Shared ID, ID5 Universal ID, and a first-party UUID — and how they lift CPMs in cookieless environments.

User ID modules allow demand partners to recognise returning visitors across domains, even in browsers that block third-party cookies. A recognised user typically generates significantly higher bids than an anonymous one. Advlume configures three complementary ID modules in every auction — all managed automatically, without any action required on your part.

Why user IDs matter

Programmatic CPMs are heavily influenced by how well a DSP can model a visitor's interests and intent. A visitor with a persistent, cross-site identity allows a DSP to apply frequency capping, retargeting, and audience segmentation — all of which increase their willingness to bid. Without a user ID, many demand partners treat the impression as completely anonymous and bid conservatively or not at all.

Third-party cookies — the traditional mechanism for cross-site identity — are blocked by Safari and Firefox by default, and were phased out of Chrome. User ID modules are the industry's response: they establish persistent, consented identifiers using first-party cookies, local storage, and privacy-preserving identity graphs.

Active modules

1. Shared ID (Prebid First-Party ID)

Property	Value
Storage	First-party cookie: `_sharedID`
Expiry	365 days
Scope	Your domain only
Requires consent	Yes — only set when TCF/GPP consent is granted

Shared ID is Prebid's built-in first-party identifier. It generates a UUID stored in a first-party cookie on your domain and passes it to every bidder in the auction. Unlike third-party cookies, it is not blocked by Safari ITP or similar browser policies. Its scope is your domain, so it enables per-site recognition without cross-site tracking concerns.

2. ID5 Universal ID

Property	Value
Storage	localStorage key: `id5id`
Expiry	90 days, refreshed every 8 hours while active
Partner ID	1645 (Advlume's registered ID5 partner)
Scope	Cross-domain (ID5's identity graph)
Requires consent	Yes — gated by TCF purpose consents

ID5 is a privacy-preserving universal identity graph. When a visitor consents, ID5 matches their browser signals against a deterministic/probabilistic graph of known users. The returned ID is shared with demand partners that are integrated with ID5, enabling cross-site audience data to flow into the auction even in cookieless environments. The ID refreshes silently in the background every 8 hours without additional user prompts.

3. Publisher-Provided ID (first-party data passthrough)

Property	Value
Storage	localStorage key: `_advlume_fpid`
Expiry	Persists until cleared (no expiry)
Scope	Your domain only
Source domain	`advlume.com` (passed as an EID)
Requires consent	No — this is a first-party technical identifier

The wrapper generates a UUID on first visit, stores it in localStorage under the key _advlume_fpid, and submits it to every bidder as a Publisher-Provided ID (EID) with source: "advlume.com" and atype: 1. This gives demand partners a stable first-party signal for frequency capping and session-level targeting, even when third-party cookies and ID5 are unavailable (e.g. Safari private mode).

If localStorage is blocked — for example in Safari's strict ITP mode or private browsing — a fresh UUID is generated in memory for the session. The ID will not persist across page loads in that case, but the auction still runs normally.

User sync

In addition to the three ID modules, Prebid performs user sync calls after the auction. These are lightweight requests that allow each demand partner to set or read their own first-party identifiers:

Both iframe and pixel (image) sync methods are permitted for all bidders.
Up to 3 syncs per bidder per page load.
Syncs are delayed by 3,000ms after the auction ends to avoid competing with content loading.
The auction itself waits up to 200ms for user sync data before proceeding.

Consent gating

All user ID resolution and user sync are fully gated on TCF and GPP consent. If a visitor does not consent to personalised advertising, Prebid will not attempt to resolve ID5 or Shared ID for that session. The first-party Advlume ID (_advlume_fpid) is a technical identifier — not a tracking cookie — and is set regardless of consent for session management purposes, consistent with the legitimate interest legal basis under GDPR.

What you see in DevTools

You can inspect the resolved IDs in the browser console before an auction runs:

pbjs.getUserIds()
// Returns something like:
// {
//   sharedId: { id: "01JXXXX..." },
//   id5id:    { uid: "ID5-XXXXX...", ext: { linkType: 2 } },
//   pubProvidedId: [{ source: "advlume.com", uids: [{ id: "xxxxxxxx-...", atype: 1 }] }]
// }