How do I decode a Base64 string online?

Paste your Base64 string into SmartDevBox at smartdevbox.com. It automatically detects Base64 encoding and decodes it instantly — no configuration needed.

How do I decode a JWT token without a secret?

Paste your JWT token into SmartDevBox. The JWT Inspector tool decodes the header and payload and displays them as readable JSON. Note: this decodes but does not verify the signature — you don't need the secret to read the claims.

How do I format or pretty-print JSON?

Paste your minified or unformatted JSON into SmartDevBox. The JSON Formatter tool detects it automatically and pretty-prints it with configurable indentation.

How do I convert a Unix timestamp to a human-readable date?

Paste a Unix timestamp (e.g. 1700000000) into SmartDevBox. The Unix Timestamp converter detects it and shows the equivalent date and time in UTC and your local timezone.

How do I convert JSON to CSV?

Paste a JSON array of objects into SmartDevBox and select the JSON → CSV tool. It converts your data to comma-separated format with headers derived from the JSON keys.

How do I compute a SHA-256 hash online?

Use the Hash Generator tool on SmartDevBox. Paste any text and it computes MD5, SHA-1, SHA-256, and SHA-512 hashes simultaneously in the browser.

How do I parse and understand a cron expression?

Paste your cron expression (e.g. "0 9 * * 1-5") into SmartDevBox. The Cron Job Parser explains it in plain English and shows the next scheduled run times.

How do I decode an X.509 certificate online?

Paste a PEM-encoded certificate (beginning with -----BEGIN CERTIFICATE-----) into SmartDevBox. The Certificate Decoder extracts and displays the subject, issuer, validity dates, public key, and extensions.

Is SmartDevBox free to use?

Yes. SmartDevBox is completely free with no account or sign-up required. All tools run in the browser. An optional AI mode (for ambiguous input detection) can be enabled with your own OpenAI API key.

Does SmartDevBox send my data to a server?

No. All tools run entirely in the browser using client-side JavaScript. Your data never leaves your machine unless you opt into the AI mode, which sends input to OpenAI for format detection.

X.509 Certificate Decoder — Inspect SSL/TLS Certs Online

Certificate Decoder parses PEM-encoded X.509 certificates (SSL/TLS certificates starting with -----BEGIN CERTIFICATE-----) and extracts the subject, issuer, validity period, serial number, and signature algorithm. All parsing runs via a pure-JavaScript ASN.1 DER decoder entirely in the browser.

Common Use Cases

Checking certificate expiry dates before renewal
Verifying the Subject CN and SAN fields of a certificate
Inspecting issuer chain information for SSL debugging
Auditing certificate serial numbers and algorithms

Frequently Asked Questions

How do I decode an X.509 certificate?

Paste a PEM-encoded certificate (starting with -----BEGIN CERTIFICATE-----) into SmartDevBox. The Certificate Decoder extracts the subject, issuer, validity period, public key algorithm, and all certificate extensions.

Is it safe to paste a certificate into an online decoder?

X.509 public certificates are designed to be public — they contain no private key material. It is safe to decode them in any online tool. Never paste a private key into an online service.

Privacy & Security

This tool runs entirely in your browser using client-side JavaScript. No data is sent to a server — your input never leaves your machine. SmartDevBox has no account system, no usage tracking, and no paid tier. See the Privacy & Security page for full details.

Base64 DecoderDecode any Base64 string back to plain text instantly in your browser. Free, no sign-up, 100% client-side. Supports standard and URL-safe Base64.
JWT DecoderDecode JWT tokens and inspect header, payload, and signature instantly. Free, no sign-up. Works without the signing secret. 100% client-side.