--- title: "Token Introspection — Identity Glossary | IDSync" description: "Token introspection is an OAuth 2.0 endpoint (RFC 7662) where a resource server asks the authorization server whether an opaque access token is still active…" lang: en json-ld: | [ { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://idsync.com/" }, { "@type": "ListItem", "position": 2, "name": "Glossary", "item": "https://idsync.com/glossary" }, { "@type": "ListItem", "position": 3, "name": "Token Introspection", "item": "https://idsync.com/glossary/token-introspection" } ] }, { "@context": "https://schema.org", "@type": "DefinedTerm", "@id": "https://idsync.com/glossary/token-introspection", "name": "Token Introspection", "alternateName": [ "RFC 7662", "OAuth introspection" ], "description": "Token introspection is an OAuth 2.0 endpoint (RFC 7662) where a resource server asks the authorization server whether an opaque access token is still active and what scopes and subject it represents.", "url": "https://idsync.com/glossary/token-introspection", "inDefinedTermSet": "https://idsync.com/glossary" }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "Introspection vs JWT validation — which should I pick?", "acceptedAnswer": { "@type": "Answer", "text": "Use JWTs for stateless, high-throughput APIs where short token lifetimes are acceptable. Use introspection (opaque tokens) when central revocation and fine-grained session control matter more than latency." } }, { "@type": "Question", "name": "Is introspection slow?", "acceptedAnswer": { "@type": "Answer", "text": "It adds one network call. With smart caching (per-token, for its TTL) the overhead is negligible for most APIs." } } ] } ] --- [![IDSync — identity software buyer platform](/assets/idsync-logo-BKS89EW4.png)](/) [Directory](/directory) [Compare](/compare) [Resources](/resources) [Browse tools](/directory)[Run Stack Finder](/stack-finder) 1. [Home](/) 2. [Glossary](/glossary) 3. Token Introspection Authorization # Token Introspection Token introspection is an OAuth 2.0 endpoint (RFC 7662) where a resource server asks the authorization server whether an opaque access token is still active and what scopes and subject it represents. Last reviewed 3 months ago Key points - Defined in RFC 7662 - Used with opaque tokens (not self-contained JWTs) - Adds a network call per request — usually cached briefly - Returns active flag, scope, sub, client\_id, exp - Alternative to JWT validation when central revocation matters ## What it is Token introspection lets a protected API ask the authorization server, _is this token still valid, and what does it grant?_ Defined in [RFC 7662](https://www.rfc-editor.org/rfc/rfc7662), it's the canonical way to validate opaque (non-JWT) OAuth access tokens. ## How it works The resource server POSTs the token to the AS's `/introspect` endpoint, authenticated as a confidential client. The AS responds with `{ active: true|false, scope, client_id, sub, exp, ... }`. The resource server then enforces scope and subject checks before serving the request. ## When buyers care - API gateways and microservices that need authoritative, revocable token state - Environments where signed JWT lifetimes are too long to safely cache - Compliance regimes that require immediate revocation on offboarding ## Common misconceptions - **Introspection is not for JWTs you can validate locally.** If you trust the signature and claims, you don't need it. - **Don't introspect on every microservice hop.** Cache the response for the token's remaining lifetime (or shorter). ## FAQ ### Introspection vs JWT validation — which should I pick? Use JWTs for stateless, high-throughput APIs where short token lifetimes are acceptable. Use introspection (opaque tokens) when central revocation and fine-grained session control matter more than latency. ### Is introspection slow? It adds one network call. With smart caching (per-token, for its TTL) the overhead is negligible for most APIs. IDSync provides educational buyer guidance based on publicly available information, editorial review, and user-submitted data. Vendor information should be verified before purchase. [Who we are, our methodology & disclosure policy](/about). ### One identity concept, explained per issue Get vendor-neutral identity explainers and market updates in your inbox. Work email\* Name Company Role (optional) Interests (optional) Pick what you want more of. IAMCIAMSSO/MFAIGA/PAMSCIM/provisioningAI agent identityVendor updatesSecurity incidents Subscribe Twice-monthly identity digest. Curated, vendor-neutral. Unsubscribe any time. ### Vendor categories [authorization](/directory/category/authorization)[api access management](/directory/category/api-access-management) ### Vendors to evaluate [auth0](/directory/auth0)[cerbos](/directory/cerbos)[permit io](/directory/permit-io) ### Not sure which tool you need? 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