This is the self-contained offline copy of the systrex CSR and certificate decoder. It decodes certificates and signing requests, and verifies a request’s self-signature, entirely inside this browser. Verify this file's SHA-256 digest against the release manifest in the systrex source repository before trusting a copy you did not build or download yourself.
Paste PEM, bare Base64, or hex; or open a .pem, .csr, .crt, .cer or .der file. The document type is detected automatically. Nothing you paste leaves this browser.
This client tool does not transmit or store what you paste. Decoding happens in this browser.
A signing request's self-signature is verified here, in this browser, because everything needed is inside the request. A certificate's signature is not verified: that requires the issuer's certificate, and this tool fetches nothing. The validity window is shown next to today's date, and the reading is yours; this page renders no verdict.
Fields written by a requester are labelled as written, not as verified. Nothing in a signing request proves identity; the issuing CA decides what ends up on a certificate.
Open the network panel before you paste, and watch: from the first character, this page sends nothing. Documents pasted here often carry internal hostnames; they stay in this browser, are not stored anywhere, and disappear with the page.
There is no private key on this page. A signing request and a certificate are both public halves; if you have been asked to paste a private key into any web tool, decline.
The CSR generator creates a request and key in this same browser, and its output screen can hand a request straight to this decoder without the request touching a URL or any storage.