Everything runs on your machine — your input is processed right here in your browser and never uploaded to any server.
Choose one or more .der/.cer/.crt files.
Check the subject chips to confirm these are the certificates you meant.
Copy the PEM output or download it as certificate.pem.
Got a binary certificate — a .der, .cer or binary .crt — that a text-hungry tool refuses to read? This converter wraps it back into standard Base64 PEM, the format Nginx, Apache, and most modern tooling expect. Drop in several files and they combine into a single PEM output, ready to use as a bundle.
Each file is genuinely parsed, not blindly re-encoded: you see the subject of every certificate as confirmation you converted the right thing, and files that are already PEM pass through untouched instead of erroring.
100% private“Files are read and re-encoded entirely in your browser — nothing is uploaded. Certificates are public data, and no private key is involved.”
Open it in a text editor: PEM starts with "-----BEGIN CERTIFICATE-----"; DER looks like binary garbage. This tool accepts either — it detects the format automatically.
Yes — select them all and the output concatenates them, which is exactly the format servers want for certificate bundles.