Search Index
A search index is the structured database where a search engine stores the content it has crawled and analyzed. When a user searches, results come from the index — not the live web — which is why unindexed pages are invisible.
Google's index is built as an inverted index: instead of storing pages as documents to scan, it maps every meaningful term to the list of documents containing it, with position, prominence, and entity annotations. This structure is what makes retrieving candidates for a query across hundreds of billions of documents possible in milliseconds.
Court filings in the 2023 US antitrust trial put Google's index at roughly 400 billion documents. Entry into the index is the outcome of search engine indexing; exit happens through quality re-evaluation, noindex directives, 404/410 responses, or deduplication into a different canonical URL.
The index is not a single uniform store. Google tiers it by how often documents are accessed and refreshed — frequently-served, frequently-updated documents live in faster storage and get recrawled more often, which is why stale or rarely-linked pages can drop out over time.
Quick facts
What does the index store for each page?
For each indexed URL, Google stores the parsed text and its term positions, the selected canonical URL, structured data and extracted entities, link annotations, freshness signals, and the signals its ranking systems read at serving time. The rendered content — after JavaScript execution — is what gets stored, not the raw HTML alone.
How do pages leave the index?
Pages leave the index when Google recrawls them and finds a noindex directive, a 404 or 410 status, a redirect, or a canonical pointing elsewhere — or when quality re-evaluation demotes them below the indexing threshold. Deindexing from quality re-evaluation is gradual and shows up in Search Console as a shrinking indexed-page count.
Frequently Asked Questions
Is the Google index the same as the web?+
No. The index is the subset of the web Google has crawled, analyzed, and judged worth storing. Large parts of the web — blocked, duplicative, low-quality, or undiscovered pages — are not in it.
Why did my page disappear from the index?+
Check the URL in Search Console's URL Inspection tool. The usual causes are an accidental noindex, a canonical pointing to another URL, a server error during recrawl, or quality re-evaluation after a core update.