Certificate decoder, .reg file viewer and unknown file identifier
A certificate decoder browser tool, a registry file viewer and a file identifier that read your file on your own machine. Nothing is uploaded, nothing is installed, and there is no size limit.
Four steps
How the certificate decoder works in your browser
Same pipeline for all three tools. The file is read where it already sits, the fields are printed from the bytes, and the limits are printed next to them.
Drop the file on the tool page
The file stays on your computer. Parsing happens on a background thread using byte-range reads, so a big PFX bundle or a long registry export is handled the same way as a two kilobyte certificate.
Read the fields, not a verdict
For a certificate you get subject, issuer, validity dates, subject alternative names and fingerprints. For a .reg you get every key, the value type and where it lands in the registry. For an unknown file you get the format the magic bytes say it is.
Read the limits printed with the result
Offline there is no revocation check, and the issuer signature is not proven against a trusted root. The .reg viewer never stamps a file safe. Knowing the format of a file is not the same as knowing the file is safe to open.
Take the report with you
Copy, download or print the output as Markdown or plain text, then paste it into a ticket, a forum post or an email to whoever issued the file. The report reads the same on their screen as it does on yours.
03
How we work
A clear path from first conversation to finished work.
BSOD Dump Analyzer
Read a blue-screen minidump or MEMORY.DMP in the browser. Returns the stop code, the blamed driver, a fix plan and the evidence behind it, and explains why ntoskrnl.exe is usually the victim rather than the root cause.
WER and App Crash Reader
Open Windows Error Reporting files and app-crash minidumps to find the faulting module and exception code. Explains that a .wer file is a summary, not a full dump.
Certificate Decoder
Decode SSL and X.509 certificates, CSRs, keys and PFX files to show subject, issuer, expiry, SANs and fingerprints. Works offline, so there is no revocation check and the issuer signature is not proven against a trusted root.
.reg File Viewer
Read a registry file before you run it, with the keys, value types and locations laid out in plain language. Never stamps a file safe, and notes that a merge cannot be undone.
We will never ask you to email us a private key or a PFX, and we will never stamp a file safe. The tool prints what is in the bytes, tells you what it cannot prove, and stops there.
Three tools
Certificates, registry files and files you cannot name
Each one parses locally, each one has its own reference library, and each one tells you where it stops.
Certificate decoder
Decodes SSL and X.509 certificates, CSRs, keys and PFX bundles to show subject, issuer, expiry, SANs and fingerprints. Because it runs offline there is no revocation check, and the issuer signature is not proven against a trusted root. Never email or paste a private key
.reg file viewer
Read a registry file before you run it. Keys, value types and locations are laid out in plain language, with the hive each change lands in. The viewer never stamps a file safe, and a merge cannot be undone, so the decision to merge is
What is this file
Identifies a file by its magic bytes from the first 4 KB rather than trusting the extension, which matters when a file has been renamed to look harmless. Knowing the format is not the same as knowing the file is safe to open.
05 — Common questions
What these three tools will not tell you
The limits matter more than the features here, so we print them in the product and repeat them on this page.
Frequently Asked Questions
- Can you check whether a certificate has been revoked?
- No. Revocation is checked by asking a CRL or an OCSP responder over the network, and nothing here goes over the network. We decode the certificate you dropped and show you the fields it carries. If revocation matters, check it with a tool that is allowed to make that call.
- Does the decoder prove the issuer signed the certificate?
- No. We read and display the issuer name, the algorithm and the signature bytes, but we do not verify the chain against a trusted root store. Treat the issuer field as a claim written in the file, not as proof.
- Should I ever send you a private key or a PFX?
- Never. Do not email one, do not paste one into a chat, and do not send one to us. The decoder reads it inside your own browser so there is no reason to hand it to anybody. If a key has already left your machine, treat it as compromised and reissue.
- If the .reg viewer opens a file, is it safe to merge?
- No. The viewer never stamps a file safe. It shows you the keys, the value types and where each change lands so you can judge it yourself. A merge cannot be undone by us or by the tool, so export a backup of the affected keys first and merge only if you understand every line.
- The file identifier named the format. Is the file safe to open?
- No. Format and safety are different questions. Magic bytes from the first 4 KB tell you what a file really is even when the extension has been renamed, which is useful, but a genuine document can still carry something you do not want to run.
- Is there a size limit, and is anything kept?
- There is no size limit, because reads are byte-range rather than loading the whole file into memory. Nothing from the file is stored or sent. Reports export as Markdown or plain text from your own browser.
Drop the certificate, the .reg or the mystery file
It is free, there is nothing to install, and the file stays on your computer while it is read.