Glossary

Quick definitions of terms used across the OG Fetch docs.

Open Graph (OG): A protocol from Facebook that lets web pages declare structured metadata via <meta property="og:*"> tags. Title, description, image, type, and site name are the most common fields. Used by Slack, Discord, Twitter, LinkedIn, and Messenger when rendering link previews.
See also: Preview API
AEO (Answer Engine Optimization): Optimizing content for answer-engine surfaces like ChatGPT, Perplexity, and Google AI Overviews. AEO scores evaluate structured data, factual density, citation-friendliness, and how easily an LLM can extract a clean answer from the page.
See also: AEO Analysis API
SEO (Search Engine Optimization): Optimizing a page to rank well in classical search results (Google, Bing). Distinct from AEO.
See also: SEO API
Structured data: Machine-readable metadata embedded in a page using formats like JSON-LD, Microdata, or RDFa. Search engines and AI agents use it to understand entities, relationships, and content type. schema.org is the canonical vocabulary.
SSRF: Server-Side Request Forgery — an attack where the user tricks a server into making requests to internal/private endpoints. OG Fetch blocks requests to private IP ranges (RFC 1918, loopback, link-local), non-HTTPS URLs, and URLs that resolve to internal hosts during DNS lookup.
Confidence score: A 0.0–1.0 (or 0–100) value indicating how sure the detection is. In the Stack endpoint, confidence reflects how many independent signals (HTML markers, headers, asset URLs, JS globals) matched a given technology.
See also: Stack Detection API
Grade: A letter (A–F) or band assigned by SEO and AEO endpoints to summarize per-metric scores. Bands are stable; underlying score thresholds may shift between minor versions — always check the numeric score, not the band, for programmatic decisions.
Cached response: A response served from OG Fetch's internal cache rather than a fresh upstream fetch. The cached boolean field on every successful response tells you which one you got. Cached responses don't count toward upstream fetch quotas; they do count toward your API call quota.
Idempotency key: A client-provided identifier that lets the receiver recognize duplicate retries and skip re-processing.