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ThumbmarkJS
Protect Product / Field guide
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ThumbmarkJS fraud detection review
Browser fingerprinting building block. Editorial score: 7.0 out of 10. Best fit for developer teams that want browser identity as a building block.
By Michael Delgado · Reviewed against the 22-criterion rubric. Product/access source checked 21 October 2026.
7.0
Editorial score / 10
Rank 20 of 20
Thumbmark provides an open-source browser library and a hosted API with visitor ID, bot and network signals. Its free and Pro quotas are API calls.
##
Where it fits
Best fit for developer teams that want browser identity as a building block. Our rating weights practical decisions, account linkage, signal depth, implementation and commercial fit. A tenth of a point is a close judgment; use the full
[methodology](/methodology/)
and your own traffic before choosing.
##
Signals, output and workflow
In a proof of concept, request a sample response for a clean user and a suspicious user. Record which fields are available to engineering, risk and support, and whether the result directly supports the action your team needs.
##
Access and pricing
Free access:
1,000 API calls / month.
Public entry price:
15 euros / month for 15,000 API calls. Products in this comparison meter different units. Calculate the number of calls your actual flow will make, confirm included products and any overage, and get the latest terms from the vendor.
##
Strength and trade-off
Strength:
Best fit for developer teams that want browser identity as a building block.
Trade-off:
A fingerprinting API still needs your own account-level rules and response workflow; evaluate the open-source and hosted offerings separately.
##
What to verify in a test
-
Run the product on the same signup, login or payment cohort you use for other candidates.
-
Count known abuse caught, legitimate users flagged, missing responses and latency.
-
Compare the output to the operational action your team can take, then normalize the quote to that event volume.
Next step:
Read the
[parallel test guide](/guides/parallel-fraud-tool-test/)
and the
[alternative shortlist](/alternatives/)
before committing to a plan.
##
Source
[Vendor page ↗](https://www.thumbmarkjs.com/pricing/)
##
FAQ
###
What is ThumbmarkJS best for?
Best fit for developer teams that want browser identity as a building block.
###
What does ThumbmarkJS cost?
15 euros / month for 15,000 API calls. Free access: 1,000 API calls / month. Check the current vendor page for plan details and billing units.
###
What should I test before adopting ThumbmarkJS?
A fingerprinting API still needs your own account-level rules and response workflow; evaluate the open-source and hosted offerings separately.
[Visit ThumbmarkJS ↗](https://www.thumbmarkjs.com/pricing/)
Review index
###
ThumbmarkJS
Browser fingerprinting building block
[How scores work ↗](/methodology/)
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