--- title: "Glossary" description: "Concise definitions of AudD-specific terms an integrator or agent will encounter: endpoints, result fields, identifiers, streams, and request parameters." slug: "/resources/reference/glossary" section: "reference" keywords: [audd, glossary, isrc, upc, audio fingerprinting, song_link] --- # Glossary Definitions of the AudD-specific terms that appear across the API, responses, and SDKs. Each entry is one concept; where an SDK uses a different name than the HTTP wire form, both are noted. ## Standard endpoint `POST https://api.audd.io/`. The default recognition method, for a short audio clip (file-size cap 10 MB). Returns a single best match, or `result: null` when nothing is recognized. Response time is under two seconds. ## Enterprise endpoint `POST https://enterprise.audd.io/`. For longer audio — full-length songs, short-form videos, podcasts, broadcasts, DJ sets — and files with multiple songs. It splits the file into chunks server-side and returns every recognized track. There is no practical file-size cap. Billing is metered per 12 seconds of audio processed, so always set `limit` during development. ## Chunk The unit the enterprise endpoint works in: each submitted file is treated as a sequence of 12-second audio chunks. The `skip` and `every` parameters control which chunks are fingerprinted, and billing is counted per chunk. ## offset In an enterprise response, `offset` is the position within the file you submitted of the start of the 12-second chunk that contains a match. It locates the chunk in the overall file. ## start_offset / end_offset In an enterprise response, these are positions in **milliseconds within the 12-second chunk** (not within the whole file) marking where the matched fragment starts and ends. Combine with the chunk's `offset` to place a match in the full file. ## timecode The position **within the matched song** at the point the submitted clip aligns to — for example, `02:32` means the clip matched the part of the recording two minutes and thirty-two seconds in. It is a position in the reference track, not an offset into the user's clip. ## score A confidence value (0–100) on each enterprise match indicating how strongly the chunk matched that track. Higher is a stronger match. Access to `score` requires a Startup plan or higher. ## ISRC International Standard Recording Code — the unique identifier of a sound recording. Returned as `isrc` on a match. Available on enterprise responses and for accounts on a Startup plan or higher. ## UPC Universal Product Code — the identifier of a release (the product the recording was published on). Returned as `upc` on a match. Like ISRC, it is available on enterprise responses and on a Startup plan or higher. ## audio_id The identifier of a track in your own custom catalog, returned on a custom-catalog match. On such matches `artist` and `title` may be null, since the catalog entry is yours to map; you track the `audio_id` → song relationship on your side. ## song_link A universal link to the recognized song's page on `lis.tn`, returned as `song_link` (for example, `https://lis.tn/Warriors`). It resolves to a page that links out to the song across services. ## lis.tn AudD's short-link domain for song pages. `song_link` values point here. ## fingerprint / audio fingerprinting The compact, content-derived signature AudD computes from audio to identify it. Recognition works by fingerprinting the submitted audio and matching the fingerprint against the database, rather than comparing raw audio. ## public database AudD's catalog of commercially released music — about 160 million songs — that the standard and enterprise endpoints match against by default. ## custom catalog A private fingerprint database attached to your account. You upload your own tracks via `POST https://api.audd.io/upload/` (special access required; email api@audd.io), and later recognition calls can match against them. Matches against your catalog carry an `audio_id`. ## return / returnMetadata The request option that asks for extra per-provider metadata blocks on a match. On the HTTP API it is the `return` form field (comma-separated identifiers such as `apple_music,spotify,deezer,musicbrainz`); the SDKs expose it as `returnMetadata` (or the language's idiomatic equivalent). Provider metadata is not available on the enterprise endpoint. ## market Request parameter that sets the country code used for Apple Music, iTunes, and Spotify results in the returned provider blocks. Defaults to `us`. ## extras / model_extra A map on each typed result and per-provider block exposing fields that the SDK does not surface as typed properties — additional fields outside the typed surface. Read beta or newly added response fields through `extras` (some SDKs name the accessor `model_extra`) without waiting for a typed property. ## stream / radio_id A stream is a continuous audio source (radio, livestream, broadcast) registered for ongoing recognition via the streams endpoints. Each stream is identified by a `radio_id`, an integer you choose to label it. A stream URL can be a direct stream URL (HLS, Icecast, m3u/m3u8) or a shortcut such as `twitch:`, `youtube:`, or `youtube-ch:`. ## callback URL The URL AudD POSTs stream recognition results to, set with `setCallbackUrl`. Each callback is a JSON payload with the recognized song. A working callback URL that returns `200 OK` must be configured for the account even if you only consume results via longpoll. ## longpoll `GET https://api.audd.io/longpoll/` — an HTTP long-polling way to receive stream results without running a callback server or holding a static IP. A callback URL must still be configured first; longpoll may never return events for an account that has no callback URL set, even when songs are being recognized. ## longpoll category The subscription key a longpoll client subscribes to, passed as the `category` parameter. It comes from the `longpoll_category` field on a stream in the `getStreams` response. You can share a category with clients without exposing your API token. ## the test token The public token `api_token=test`. It works only on the standard endpoint — not enterprise, not streams — and is limited to 10 requests per day. Use it for hello-world snippets; get your own token at [dashboard.audd.io](https://dashboard.audd.io). --- **Related** - [Result fields reference](/resources/reference/result-fields) - [Error codes reference](/resources/reference/errors) - [SDK docs](https://docs.audd.io/sdks) - [API reference](https://docs.audd.io)