Direct answer
Indexing is the analysis of retrieved content and its conversion into a usable record in a search or retrieval system. A page may be crawlable yet remain unindexed because of a noindex instruction, duplicate content, low processability, a quality decision, a technical error or the system's scope.
In plain language
A librarian may receive a book without adding it to the catalogue. Seeing the book does not mean that it received a catalogue number or will appear in a search.
Why this matters
Treating successful crawling as successful indexing leads to the wrong diagnosis. A site owner may keep adding content without investigating why a page cannot be selected despite being accessible.
Do not confuse
- Discovery, crawling, rendering, indexing and retrieval are separate states.
- robots.txt controls access; noindex is an indexing instruction.
- A public search index and an organisation's private RAG index are not the same.
What should you do?
- Check indexability signals for important URLs.
- Review noindex, canonical, redirect and HTTP status information together.
- State the preferred canonical URL clearly for duplicate pages.
- Test whether JavaScript-generated or post-access content can actually be processed.
- Where the provider offers diagnostic tools, record the dated result.
How do you audit it?
- Was the page crawled or merely discovered?
- Is there a noindex instruction or conflicting canonical?
- Is the served content empty, incomplete or behind a session?
- For which system was index status measured?
- Was presence in an index mistaken for retrieval in a particular query?
Limit
One provider's index status says nothing about another provider's index. Indexing does not guarantee use in a particular answer.
Remember in one sentence
Crawling gets through the door; indexing enters the item in the catalogue.
Sources for this record
- S03Google Search Central, *Overview of Crawling and Indexing*Provider documentation
- S04Google Search Central, *Block Search Indexing with noindex*Provider documentation
- S11Google Search Central, *Canonicalization*Provider documentation