Short answer
Choose jwt.io when you need to verify a signature with a secret or a public key, or to generate a token. Choose Blobster when you only need the header and claims of a real token and want it to stay in a local extension.
Key points
- jwt.io verifies signatures with a shared secret or a public key in PEM or JWK form, and its encoder signs new tokens.
- Blobster shows the decoded header and payload, readable
exp,iatandnbftimes, and warnings for expired tokens andalg: none. Signatures stay unverified. - jwt.io is presented by Auth0 and published under Okta’s copyright. Its privacy choices notice says personal information may be shared with third-party ad partners, for example through cookies.
- Decoding needs no key. The risk in pasting a live token anywhere is the token itself, which works for whoever holds it until it expires.
At a glance
| Criterion | Blobster | jwt.io |
|---|---|---|
| Decode header and payload | Yes, inside the extension | Yes |
| Verify signature | No, shown as unverified | Yes, with a secret or a PEM or JWK public key |
| Create or sign tokens | No | Yes, with the JWT Encoder |
| Claim help | Readable exp, iat and nbf; warnings for expiry and alg: none | Claims breakdown with descriptions of registered claims |
| Other data | JSON, YAML, HAR, NDJSON, OpenAPI and more in the same workbench | Focused on JWTs |
| Account and tracking | No account, analytics or telemetry | No account needed; Okta’s privacy policy and cookie choices apply |
Where jwt.io is stronger
jwt.io answers the question Blobster leaves open: is this token genuine? Paste the token, add the secret or public key, and the debugger reports whether the signature verifies. Its encoder goes the other way and signs a new token from a header, a payload and a key, which helps when you build test fixtures.
It also explains claims. The claims breakdown describes registered claims such as at_hash, nonce and auth_time and links to the specifications, and the site has an introduction to JWTs and a list of libraries for each language.
Where Blobster is different
Blobster is for reading the tokens that turn up while you debug something else: in a log line, a HAR capture, an API response or a config file. Paste or open the token and Blobster shows the header and payload, turns exp, iat and nbf into readable times, and warns when the token has expired or uses alg: none.
It runs as a browser extension with no account, analytics, telemetry or share link, so a production token stays on your machine. In Chrome you can also select a token on a page, right-click and open it in Blobster.
Decoding is not the sensitive part
A signed JWT is encoded, not encrypted. jwt.io’s own introduction says the information in a signed token is readable by anyone and that secret information does not belong in the payload unless the token is encrypted.
The sensitive part is the token itself. A bearer token works for whoever holds it until it expires or is revoked, so pasting a production token into any website means trusting that site with a working credential. Decoding it locally avoids the question.
Use both, in order
Read the claims locally first. Most questions, such as which audience, which scopes or when the token expires, end there. When you do need to check a signature, use jwt.io with a token from a test environment or one that has already expired, or verify it in code with one of the libraries jwt.io lists.