Ajv
Ajv: A highly capable validator for JavaScript teams that need deep schema support. Ranked #18 of 29 in JSON Tools by our editors (7.4/10); pricing: Free plan; best for javaScript applications needing deep schema validation.
At a glance
- Editor score7.4 / 10
- PricingFree plan
- Best forJavaScript applications needing deep schema validation
- Free planYes
- Paid fromFree
- Schema validationYes
- Facts checked21 Sep 2026
Where it wins
- Supports JSON Schema drafts 04, 06, 07, 2019-09, and 2020-12
- Compiles schemas into JavaScript validators and standalone code
- Adds recursive schemas, custom keywords, async validation, and JTD parsers
Where it doesn't
- Focused on JavaScript applications rather than a general-purpose tool
- Command-line workflows require the separate ajv-cli package
- Its extensive schema options may exceed simpler validation needs
Our verdict on Ajv
Ajv is an open-source JavaScript library for validating JSON data against JSON Schema and JSON Type Definition schemas. It is intended for developers working with API payloads, configuration files, and other JavaScript data across browser, Node.js, and command-line workflows. The library supports web-based JavaScript applications and offers a free plan under its open-source pricing model.
Schema coverage is the standout strength. Ajv supports JSON Schema drafts 04, 06, 07, 2019-09, and 2020-12, along with JSON Type Definition. It can compile schemas into JavaScript validation functions and generate standalone validation code. Referenced and recursive schemas support more involved data models, while custom keywords and formats extend validation rules. Asynchronous validation is available for user-defined formats and keywords, and JTD schemas can produce compiled JSON parsers and serializers. These capabilities make Ajv a strong fit when validation depth and generated JavaScript code matter more than a minimal API.
Ajv also covers operational workflows through command-line validation of multiple data files, although that workflow uses the separate ajv-cli package. Its open-source model suits teams that want a library they can incorporate into JavaScript applications without a paid-plan structure. The trade-off is focus: Ajv is specialized around JSON validation and JavaScript, so a simpler validator may be a better choice for basic schemas or teams seeking a narrower set of configuration options. Choose Ajv when draft coverage, schema references, custom rules, asynchronous checks, or compiled output are central requirements.
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Ajv pricing
Ajv fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Schema validation | Yes |
| JSONPath querying | Not verified |
| jq querying | Not verified |
| Batch processing | Yes |
| JSON diff and compare | Not verified |
| Available platforms | web |
| Deployment | Cloud |
| Platforms | Web |
| Support | Docs |
| Built for | Solo, Small business, Mid-market, Enterprise (editorial estimate) |
| Pricing | Free plan |
| Website | ajv.js.org |
| Facts checked | 21 Sep 2026 |
Alternatives to Ajv
- BracketViewA broad JSON toolkit with querying, schemas, diffs, snapshots, and webhook testing.9.4
- JSON CrackA broad, free toolkit for visualizing, querying, validating, and converting structured data.9.2
- jsonfmt.devA broad JSON toolkit with local browser processing, API access, and a $9 one-time Pro plan.9.0
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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