Detect Secrets and API Keys in Text with Regex

Every few months someone commits a Slack bot token to a public GitHub repo, an API key appears in a Stack Overflow post, or a production config leaks in a support ticket screenshot. Automated scanners catch some of these - but not all. And the ones that slip through often do so because a regex was too loose, too strict, or tested against the wrong kind of input.

This guide covers what makes secret detection regex actually work: realistic patterns for common credential formats, the false positive problem that makes blind scanning unreliable, and a repeatable process for building detection logic you can trust.

If you want to test patterns as you read, open Toolblip's Regex Tester and paste your candidate patterns. For breaking down a complex pattern into plain English, use the Regex Explainer.

Why Simple Regex Fails for Secret Detection

Most developers start with something like this:

[A-Za-z0-9]{20,}

The intent: find a long alphanumeric string that looks like an API key. The result: matches email addresses, UUIDs, base64 strings, version numbers, and commit hashes - none of which are secrets.

A secret detection pattern needs to match the format of a credential, not just any long string. That means understanding what each credential type actually looks like.

Common Secret Formats and Their Patterns

GitHub Personal Access Token

ghp_[a-zA-Z0-9]{36}

GitHub PATs start with ghp_ followed by 36 alphanumeric characters. This prefix makes them relatively easy to detect without excessive false positives.

const pattern = /ghp_[a-zA-Z0-9]{36}/g;

const test = "Generated token: ghp_1a2b3c4d5e6f7g8h9i0j1k2l3m4n5o6p";
console.log(pattern.test(test)); // true

AWS Access Key ID

AKIA[0-9A-Z]{16}

AWS key IDs always begin with AKIA followed by 16 uppercase letters or digits. Note that this detects the ID only - the secret key itself is a 40-character string without a reliable prefix for detection.

const awsPattern = /AKIA[0-9A-Z]{16}/g;

const configLine = "AWS_ACCESS_KEY_ID=AKIAIOSFODNN7EXAMPLE";
console.log(awsPattern.test(configLine)); // true

Generic API Key (common vendor patterns)

Many API keys follow a pattern of a prefix + long alphanumeric string. Some common formats:

// Stripe keys (sk_live_...)
const stripePattern = /sk_live_[a-zA-Z0-9]{24,}/g;

// OpenAI API keys (sk-...)
const openaiPattern = /sk-[a-zA-Z0-9]{48}/g;

// SendGrid keys (SG....)
const sendgridPattern = /SG\.[a-zA-Z0-9_-]{22}\.[a-zA-Z0-9_-]{43}/g;

JWT Tokens

JWTs are Base64-encoded but distinguishable by structure: three dot-separated Base64URL segments.

const jwtPattern = /eyJ[a-zA-Z0-9_-]+\.eyJ[a-zA-Z0-9_-]+\.[a-zA-Z0-9_-]+/g;

This is useful for detecting accidentally-exposed tokens in logs, configuration files, or paste sites. Note: matching the structure does not mean you can decode and read the payload without the signature - but detecting the presence of a JWT is still valuable for security audits.

Generic Bearer Tokens in Headers

Bearer [a-zA-Z0-9_-]{20,}

Authorization headers often contain long bearer tokens. Detecting Bearer followed by a substantial token string catches many API key leaks without matching short session IDs.

const bearerPattern = /Bearer\s+[a-zA-Z0-9_-]{20,}/gi;

const logLine = "Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9";
console.log(bearerPattern.test(logLine)); // true

Private Key Files

SSH and private key headers are distinctive:

// SSH private key
const sshKeyPattern = /-----BEGIN (RSA |DSA |EC |OPENSSH |PGP )?PRIVATE KEY-----/g;

// GCP service account JSON
const gcpSaPattern = /"type":\s*"service_account"/g;

Database Connection Strings

Connection strings with embedded credentials are a common leak:

// PostgreSQL
const pgConnPattern = /postgres(?:ql)?:\/\/[^:]+:[^@]+@/g;

// MySQL
const mysqlConnPattern = /mysql:\/\/[^:]+:[^@]+@/g;

// MongoDB
const mongoConnPattern = /mongodb(?:\+srv)?:\/\/[^:]+:[^@]+@/g;

These patterns match connection strings containing a username and password before the @ symbol. They are useful for scanning configuration files, backup scripts, and deployment manifests.

The False Positive Problem

A detection pattern that fires on everything fires on nothing useful.

Consider a security scanner that flags every 20+ character alphanumeric string as a potential secret. Running it against a codebase produces thousands of false positives: code comments, error messages, version strings, and git commit hashes. The team starts ignoring the scanner. Real leaks stop surfacing.

The key is specificity:

Pattern	Matches	Does Not Match
`AKIA[0-9A-Z]{16}`	AWS key IDs	Email addresses, generic strings
`ghp_[a-zA-Z0-9]{36}`	GitHub PATs	Short tokens, UUIDs
`sk-[a-zA-Z0-9]{48}`	OpenAI keys	Generic 40-char strings

Test your patterns against realistic non-secret text. A good detection pattern should have high precision (few false positives) and reasonable recall (catches the target format).

Context-Aware Detection: When Format Is Not Enough

Some credential formats are ambiguous on their own. A UUID looks like many other things. A 32-character hex string could be an MD5 hash, a database ID, or a password reset token.

For these cases, context matters. A few heuristics:

Surrounding keywords - Words like password, secret, token, key, api, auth, bearer, credential in the surrounding text raise the probability that a matched string is actually a secret.

// Look for secrets near keyword context
const contextAwarePattern = /(?:api[_-]?key|secret|password|token|auth|bearer)\s*[:=]\s*['"]?([a-zA-Z0-9_-]{20,})/gi;

File path or variable name - In code, secrets often appear in variables named API_KEY, SECRET_TOKEN, AWS_SECRET, or PRIVATE_KEY. Scanning variable assignments alongside the values can reduce false positives significantly.

Entropy analysis - High randomness (long alphanumeric strings with no repeated patterns) is more characteristic of cryptographic keys than of IDs or version numbers. This is a more advanced technique, but worth noting for targeted scanning tools.

Scanning Binary and Text Files

Real secret leaks happen in more places than .env files:

Log files - Request logs, application logs, and debug output often contain authorization headers with bearer tokens
Configuration dumps - CI/CD pipeline configs, Terraform files, Kubernetes manifests
Database backups - SQL dumps with connection strings
Chat transcripts - Slack messages, support tickets, Stack Overflow posts with code samples

For scanning a text file in a browser, copy the content and use Toolblip's Regex Tester to run your patterns and see highlighted matches. For longer multi-file scanning, a CLI tool or CI integration is more practical.

For parsing nested JSON strings (like a log line containing a stringified JSON payload with an embedded token), use Toolblip's JSON Path Tester to extract and inspect the relevant fields.

What Regex Cannot Do

A regex pattern can tell you a string looks like a secret. It cannot tell you whether that string is:

Actually active or already revoked
A production key or a test key
Present in a private repository or a public one
Being used maliciously or just sitting dormant

Detection is the first step. Response and remediation are separate workflows. Consider combining regex detection with:

A secret scanning service (GitHub Secret Scanning, GitLab Secret Detection, TruffleHog)
Rate limiting and key rotation policies
Immediate revocation and re-issuance procedures

Regex is fast and useful for initial detection. It is not a substitute for a full secrets management strategy.

A Practical Detection Checklist

Before shipping any secret detection logic, verify:

Pattern matches the target format (tested against known samples)
Pattern does not fire on common non-secret strings in your codebase
Detection works in relevant file types: source code, configs, logs, JSON/YAML payloads
Matched strings are confirmed as secrets by a human before triggering alerts
The detection does not accidentally log or exfiltrate the detected secrets (ironic but common)
Revocation and rotation procedures are documented for each secret type you detect

Regex Patterns for Common Secret Types

Quick reference for the patterns discussed in this guide:

const patterns = {
  githubPat: /ghp_[a-zA-Z0-9]{36}/g,
  awsAccessKey: /AKIA[0-9A-Z]{16}/g,
  stripeKey: /sk_live_[a-zA-Z0-9]{24,}/g,
  openaiKey: /sk-[a-zA-Z0-9]{48}/g,
  jwt: /eyJ[a-zA-Z0-9_-]+\.eyJ[a-zA-Z0-9_-]+\.[a-zA-Z0-9_-]+/g,
  bearerToken: /Bearer\s+[a-zA-Z0-9_-]{20,}/gi,
  sshPrivateKey: /-----BEGIN (RSA |DSA |EC |OPENSSH |PGP )?PRIVATE KEY-----/g,
  genericApiKey: /(?:api[_-]?key|secret|password|token|auth|bearer)\s*[:=]\s*['"]?([a-zA-Z0-9_-]{20,})/gi
};

Test these against your actual codebase before relying on them. Adjust length thresholds based on the credential formats used by your vendors and infrastructure.

Browser-Based Secret Scanning

For quick ad-hoc scans - a pasted log file, a config snippet, a code fragment - browser-based tools are practical because nothing leaves your machine. Toolblip's Regex Tester runs entirely client-side, so sensitive content you paste for scanning never hits a server.

This is especially relevant for:

Scanning production log excerpts you cannot share externally
Checking a configuration file before sharing it in a support ticket
Verifying that a code snippet in a Stack Overflow question does not contain live credentials

For teams processing large codebases, integrating secret detection into a CI pipeline with proper secret management is the sustainable approach. For one-off checks and emergency situations, a browser tool closes the gap.

Related Tools

Regex Tester - Test detection patterns against sample text
Regex Explainer - Break down complex patterns into readable English
JWT Decoder - Inspect decoded JWT payloads without sending the token anywhere
Hash Identifier - Check which algorithms a digest might use
Base64 Encoder/Decoder - Decode embedded credentials in Base64 strings