This ranking covers encyclopedias, dictionaries, academic publishers, research databases, how-to libraries and other reference websites tracked by Site Worth Checker, sorted by estimated worth. Every domain links to its report with modelled traffic, potential revenue and the signals behind the estimate.
Reference sites are an unusual case for a valuation model. Many of the biggest are run by non-profits or universities, carry no advertising and are never going to be sold, so a dollar figure here means “what this much traffic would be worth to a typical ad-supported publisher”, not what the organisation would accept. Our model has no special revenue assumption for reference content: it values these domains with the general content rate, so their position comes almost entirely from Tranco rank, domain age and technical quality.
Language editions and sister projects (for example, a wiki and the foundation that runs it) appear separately when we track them, because each has its own rank. Publisher platforms such as journal hosts often rank highly because researchers and libraries visit them every day, even though most readers never see the brand. To value a reference or education site you actually own, a profit-based approach is more reliable; our website valuation guide explains how buyers price content sites.
| # | Website | Estimated worth | Tranco rank |
|---|---|---|---|
| 1 | wikipedia.org | $1B | #36 |
| 2 | sciencedirect.com | $190M | #224 |
| 3 | researchgate.net | $188M | #227 |
| 4 | wikimedia.org | $186M | #229 |
| 5 | imdb.com | $161M | #267 |
| 6 | nature.com | $145M | #297 |
| 7 | wiley.com | $132M | #325 |
| 8 | oup.com | $98.7M | #559 |
| 9 | arxiv.org | $95.4M | #457 |
| 10 | fandom.com | $92.5M | #473 |
| 11 | biblegateway.com | $75.7M | #888 |
| 12 | ieee.org | $71.5M | #617 |
| 13 | ted.com | $67.7M | #824 |
| 14 | iso.org | $66.6M | #668 |
| 15 | britannica.com | $64.6M | #682 |
| 16 | cambridge.org | $63.9M | #691 |
| 17 | plos.org | $30.9M | #1,170 |
| 18 | wiktionary.org | $26.6M | #1,351 |
| 19 | elsevier.com | $25.7M | #1,403 |
| 20 | pewresearch.org | $24.7M | #1,834 |
| 21 | wikihow.com | $23.2M | #1,944 |
| 22 | sciencemag.org | $18.7M | #1,927 |
| 23 | about.com | $17.9M | #2,040 |
| 24 | wikia.com | $14.3M | #2,542 |
| 25 | gutenberg.org | $14.2M | #2,560 |
| 26 | howstuffworks.com | $12.4M | #2,944 |
| 27 | urbandictionary.com | $12.4M | #3,662 |
| 28 | instructables.com | $11.3M | #3,209 |
| 29 | answers.com | $9.9M | #4,617 |
| 30 | thoughtco.com | $5.8M | #6,216 |
How this list is built: every row comes from a stored Site Worth Checker estimate, refreshed as domains are re-checked, so the table updates on its own. Values are model estimates from public signals (Tranco rank, modelled traffic and revenue, domain and technical factors), not appraisals or market caps. We leave out subdomains, CDN and asset hosts, link shorteners and adult sites so the list stays about websites people actually visit. Read how we estimate website worth or the background on why we use Tranco instead of Alexa rank.
Want a number for a site that isn’t listed? Check any domain free or estimate its visitors with the website traffic estimator.