OpenAnyFile
What is a .der file?
DER-Encoded Certificate is a certificate and key format developed by ITU-T (X.690), first released in 1994. It is usually created by OpenSSL, Java, Windows.
Binary ASN.1 — the same certificate as PEM without the base64 wrapping. Decoded here into subject, issuer and dates.
File details
| Full name | DER-Encoded Certificate |
|---|---|
| Category | Certificates & keys |
| MIME type | application/x-x509-ca-cert |
| Signature (magic bytes) | 30 82 (ASN.1 SEQUENCE) |
| Developer | ITU-T (X.690) |
| Introduced | 1994 |
| Opens with | Signature and certificate decoder |
| Uploaded? | No — read locally in your browser |
How to open a .der file
OpenAnyFile routes .der files to its signature and certificate decoder, which shows the certificates, and any signed file inside ready to open.
- Drop your .der file on the box above, click it to choose the file, or paste it with Ctrl+V.
- The real format is detected from the file's first bytes — not just its name.
- The file opens in the signature and certificate decoder.
- Use fullscreen for a closer look, check its checksums, or download it back unchanged.
What works — and what does not
Works
Viewing and inspecting: the certificates, and any signed file inside ready to open. Size, type, signature and checksums are always shown.
Does not work
Editing and saving back. OpenAnyFile is a viewer, not an editor — for changes you still need the original app.
Is it safe to open a .der file online?
Here, yes — because nothing is uploaded. Most "online viewers" send your file to their server. OpenAnyFile reads it with your browser's File API and decodes it on your own device, so there is no copy anywhere else. You can check: open your browser's network tab while opening a file — no upload appears.
Questions about .der files
Can I open a .der file without installing software?
Yes. OpenAnyFile opens .der files in your browser using its signature and certificate decoder. You get the certificates, and any signed file inside ready to open, with nothing installed and no account.
How do I know a file is really a .der file?
Check its first bytes instead of its name. A genuine DER file begins with 30 82 (ASN.1 SEQUENCE). OpenAnyFile shows the detected type, so a renamed file is easy to spot.
Is my .der file uploaded anywhere?
No. The file is read locally by your browser and never sent to a server — it even works offline once the page has loaded.
Does it work on phones?
Yes — on Android and iPhone, in any modern browser. You can also install OpenAnyFile as an app.
Related formats
Other formats from the same family:
Format facts checked and page updated on September 25, 2026.