What percentage of the web is indexed by search engines?

How to get close to this number

Read the question rather than the slug: it asks what share of the web search engines index. Think about what a crawler can reach — a public page with no login and no paywall — and then about how much of the web sits behind one of those. The indexable share has to be small.

The categories in the explanation are the useful breakdown: the unindexed remainder is databases, private accounts, corporate intranets and paywalled content. Your email, your bank statements and every company's internal systems are all on the web and none of them is searchable, which is where the bulk of the volume sits.

The confusion the question corrects is worth stating plainly: the deep web and the dark web are not the same thing. The deep web is everything not indexed, which is most of it and entirely mundane; the dark web is a deliberately anonymised network that is a tiny fraction of that remainder. Conflating the two makes an ordinary fact about login pages sound sinister.