How We Compare Data Annotation Tools
We compare data annotation tools on facts their makers publish: the docs, the pricing page, the code repository and the changelog. Each fact is saved with the date we read it, and each list says when it was last checked.
The 8 checks we use to compare data annotation tools
We compare data annotation tools with the same 8 checks on every page. A tool gets a check only when its own documentation says so, and a ranked list puts the tools with the most documented checks first. Ties go to the tool with more depth for that page: more kinds of data on the home and platforms pages, more label types on the image and text pages, more tracking features on the video page. Then alphabetical order decides.
| Check | What counts |
|---|---|
| Free way to start | An open-source or free-to-use edition, or a free plan on the pricing page. A time-limited trial or an academic-only license doesn't count. |
| Runs outside the vendor's cloud | The docs offer a way to run it outside the vendor's cloud: in the browser with files kept local, a desktop app, your own server, your own cloud account or on-premises. |
| AI-assisted labeling | The docs describe model-assisted labeling: pre-labels from a model, interactive segmentation such as SAM, or automatic tracking. |
| Review or QA step | The docs describe a review stage, reviewer roles, consensus or benchmark checks. A one-person 'mark as done' flag doesn't count. |
| Two or more export formats | The docs list two or more export formats, such as COCO, YOLO, Pascal VOC, CoNLL or JSON. |
| Updated in the last 12 months | Open-source tools: a release or a code push in the 12 months before the check date. Commercial tools: sold and documented today. A free tool with no dated update gets no check. |
| Price on the page | The pricing page shows a number for at least one paid plan, or the tool costs nothing and has no paid plan to buy. |
| SOC 2, ISO 27001 or HIPAA claim | The vendor's own pages (security or trust page, docs, FAQ or plan pages) state SOC 2, ISO 27001 or HIPAA compliance outright; 'designed to comply' doesn't count. We list the claim; we don't audit it. |
The checks measure what a tool documents, not how well it works in your hands. A tool with fewer checks can still be the right pick, which is why every entry also names the kind of data it handles, where it runs, its price and its biggest catch.
Where the tool facts come from
The tool facts on this site come from public pages published by each tool's maker. For open-source projects that means the code repository: its license, its latest release and whether it has been archived, read through the public GitHub or GitLab interface. For commercial products it means the documentation, the pricing page, the security or trust page and the changelog.
- Prices are copied as printed, with their billing basis (per user per month, per labeling unit, billed yearly) and the date we read them.
- Security claims such as SOC 2 Type II, ISO 27001 or HIPAA are the vendor's own words from its security page, trust center, docs or FAQ. We list them; we don't audit them.
- Third-party lists, review sites and forum threads point us to tools worth checking, but we never take a fact from them.
- When a page leaves a question open, such as a price behind a sales call, the entry says so instead of guessing.
What our tool comparisons do not claim
Our tool comparisons do not claim hands-on testing. We have not opened accounts, started free trials or booked demos for the tools on this site, so nothing here says a tool is fast, easy or accurate in use. There are no star ratings, no user reviews and no invented scores. If we test a tool hands-on in the future, the entry will say what we did and when.
Archived and discontinued annotation tools
Archived and discontinued annotation tools leave the ranked lists, because a tool that no longer gets fixes is a risk for new projects. We still name them where people search for them, with the date or the notice that ended work on them, since older guides keep recommending them.
How this site makes money
This site makes money in two ways, and neither one changes a ranked list or a fact. First, some tool makers run affiliate or referral programs; if we join one, links to that tool can earn a commission, and those links are marked as sponsored in the page code. Second, each page can carry one featured placement, sold to a tool maker, shown above the ranked list and labeled "Sponsored" in plain view. As of November 8, 2026, the site carries no affiliate links and no sponsored placements.
Image credits for this site
The image credits below cover every photo on this site. All of them are sample images that ship with scikit-image, the open-source Python imaging library, and each one is in the public domain, released under CC0, or marked as having no known copyright restrictions. The boxes, outlines, masks and points drawn on them were made for this site.
- Home page LiDAR scene: a 64-beam LiDAR sweep simulated for this site from a street built in 3D (126,002 points, 14 cuboids); no real sensor data.
- Greek coins from Pompeii: Brooklyn Museum Collection, no known copyright restrictions, via scikit-image.
- Hubble eXtreme Deep Field: NASA, public domain, via scikit-image.
- Rocket launch (DSCOVR on Falcon 9): SpaceX, released in the public domain, via scikit-image.
- Human retina: Wikimedia Commons, CC0 1.0 public domain dedication, via scikit-image.
- The boxes, outlines, masks and points on these photos were made for this site, by hand or with open-source scikit-image code.