Free patent search
Search every patent ever filed, free.
You don't need a $5,000 prior-art search to start. The world's largest patent databases are free, and a serious 4-hour search will catch most relevant prior artprior artEarlier patents, publications, or products that existed before this patent's filing date. Patent claims must be novel over the prior art.Read more → that matters. Here's where to look and how.
01 — Where to search
Six free databases that actually matter
These cover roughly 99% of the world's patent literature between them. Pick your starting point based on what you're trying to do.
Best for
Fastest search experience — full-text across U.S., EP, WO, JP, CN, and more. Best starting point for almost any prior-art search.
Watch out
Some non-Latin language patents are machine-translated. Read the original when accuracy matters.
Best for
The official U.S. database. Supports complex Boolean queries with classification codes (CPC, USPC).
Watch out
Interface is dated. Slower than Google Patents for casual browsing — but more authoritative for legal use.
Best for
European Patent Office database with strong coverage of EP, WO (PCT), and CN patents. Excellent classification tools.
Watch out
Search syntax differs from Google. Worth learning if your invention may face EPO examination.
Best for
Plain-English summaries, claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → breakdowns, and 'does NOT cover' analysis. Best for understanding what a patent actually means, not just finding it.
Watch out
Index focused on landmark and influential patents — not every grant in existence.
Best for
Free academic and patent search with structured data, citation analytics, and biological sequence search.
Watch out
Requires free registration for some features. Lens.org is also a research project — coverage updated regularly.
Best for
International PCT applications + national filings from 80+ offices. Useful for global FTO scoping.
Watch out
Interface and search refinement is functional but less polished than Google Patents.
02 — How to search
Six tactics that find more
- 01
Start broad, then narrow.
Search 5–10 plain-English phrases describing your invention. Watch for recurring terms in the results — those are the words the patent literature actually uses for your idea. Pivot your search to those terms.
- 02
Mine the CPC codes.
Once you find one or two highly-relevant patents, look at their CPC classifications. Search those classifications directly to find more patents in the same space — many of which won't surface from keyword search alone.
- 03
Read the backward citations.
Each patent lists 'References Cited' — earlier work the examinerexaminerThe USPTO official who reviews a patent application and decides whether to grant it.Read more → considered. Reading those is one of the fastest ways to find truly relevant prior artprior artEarlier patents, publications, or products that existed before this patent's filing date. Patent claims must be novel over the prior art.Read more → that share keywords or classifications.
- 04
Read the forward citations.
On Google Patents, 'Cited by' shows later patents that cited the one you're reading. This is how you walk forward through the field's evolution — and how you catch what's happened since the original was granted.
- 05
Don't stop at patents.
Prior artprior artEarlier patents, publications, or products that existed before this patent's filing date. Patent claims must be novel over the prior art.Read more → includes anything publicly available before your filing datefiling dateThe day the patent application was submitted to the USPTO. Sets the priority date for prior-art comparisons.Read more → — published papers, conference talks, product manuals, GitHub repos, ArXiv preprints, even YouTube demos. The examinerexaminerThe USPTO official who reviews a patent application and decides whether to grant it.Read more → will check; you should too.
- 06
Document what you searched.
Keep notes on which databases, queries, and date ranges you used. Patent attorneys appreciate the work, and a documented good-faith search can reduce willfulness damages if you later end up in litigationlitigationA lawsuit over patent infringement. Litigated patents often signal commercial importance.Read more →.
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