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Bearer Token Generator

Generate secure random bearer tokens for OAuth 2.0, API authentication, and access control with multiple encoding formats

[ Bearer Tokens - Quick Summary ]

What: Generate cryptographically secure random bearer tokens for OAuth 2.0 and API authentication. Supports multiple formats (Base64URL, Base64, Hex, Alphanumeric) with configurable byte lengths (16-128 bytes, 128-1024 bits of entropy). Uses CSPRNG for maximum unpredictability.

When to use: OAuth 2.0 access token generation, REST API authentication headers, session management tokens, microservices authorization, API security testing. Bearer tokens are transmitted as "Authorization: Bearer <token>" in HTTP headers to grant access to protected resources without credentials on each request.

Example: yH3kT9mN5pQ2xR7jL4wV6sZ8aB1cD0eF (Base64URL, 32 bytes, 256 bits entropy)

Security/Important: FOR TESTING ONLY. Generated with PHP random_bytes (CSPRNG) for cryptographic security. Use minimum 32 bytes (256 bits) for production. Always transmit over HTTPS only - never HTTP. Implement short token lifetimes (1 hour typical) with refresh tokens for extended sessions. Store server-side with encryption at rest. Never store in localStorage (XSS vulnerable) - use httpOnly cookies for web apps. Implement token revocation and rate limiting.

Our bearer token generator creates secure random bearer tokens for OAuth 2.0 authentication, API access control, and session management. Generate bearer tokens in multiple formats (Base64URL, Base64, Hex, Alphanumeric) with configurable byte lengths (16-128 bytes) using cryptographically secure random number generation (CSPRNG). Perfect for OAuth 2.0 implementations, REST API authentication, access token generation, and API security testing. Bearer tokens are used in HTTP Authorization headers (Authorization: Bearer ) to grant access to protected resources without requiring credentials with each request. Use our generator for secure bearer token creation in OAuth servers, API development, authentication systems, microservices authorization, and testing authentication flows. All tokens use CSPRNG for maximum unpredictability and security.

What is a Bearer Token Generator?

A bearer token generator creates secure random tokens used for OAuth 2.0 authentication and API access control. Bearer tokens are the most common type of access token in OAuth 2.0, transmitted in HTTP Authorization headers as "Bearer " to grant access to protected resources. Unlike JWT tokens which contain encoded claims and signatures, bearer tokens are simple random strings - the authorization server maintains the association between the token and user permissions. Our generator uses cryptographically secure random number generation (CSPRNG via PHP's random_bytes) to ensure tokens are unpredictable and secure against brute-force attacks.

Our generator supports multiple encoding formats: Base64URL (RFC 4648, URL-safe, no padding) is the OAuth 2.0 standard, Base64 (traditional with + and /), Hex (lowercase hexadecimal), and Alphanumeric (0-9, a-z, A-Z only). Token byte length is configurable from 16 bytes (128 bits) to 128 bytes (1024 bits), with 32 bytes (256 bits) recommended for most applications balancing security and performance. Use bearer token generation for OAuth 2.0 server development, API authentication testing, access token generation, session management, microservices authorization, and security testing. All tokens include entropy calculations and strength assessments to ensure adequate security.

Bearer Token Generator Configuration

Count (1-50 Tokens)

Specify how many bearer tokens to generate (maximum 50). Each token is cryptographically unique using PHP's random_bytes function (CSPRNG). Multiple tokens are useful for testing token rotation, load testing authentication systems, generating API credentials for multiple users, and creating test fixtures for OAuth 2.0 implementations.

Byte Length (16-128 bytes)

Control token entropy by selecting byte length before encoding. 16 bytes (128 bits) minimum, 32 bytes (256 bits) recommended for most applications, 64 bytes (512 bits) for high-security applications, 128 bytes (1024 bits) maximum. Longer tokens provide more entropy but result in longer HTTP headers. Balance security needs with practical transmission constraints.

Encoding Format

Choose output encoding: Base64URL (RFC 4648, URL-safe, recommended for OAuth 2.0), Base64 (traditional encoding with + and /), Hex (lowercase hexadecimal), or Alphanumeric (0-9, a-z, A-Z only). Base64URL is the OAuth 2.0 standard as it's safe in URLs and doesn't require additional escaping in HTTP headers.

How to Generate Bearer Tokens

[STEP 1] Configure Token Parameters

Choose count (1-50 tokens) and byte length (16-128 bytes). For OAuth 2.0 access tokens, use 32 bytes with Base64URL encoding. For high-security applications requiring strong entropy, use 64 bytes. For simple API authentication, 16-32 bytes is sufficient. Consider your security requirements and HTTP header size constraints.

[STEP 1] Select Encoding Format

Choose Base64URL for OAuth 2.0 compliance and URL safety (recommended). Use Base64 for compatibility with legacy systems. Select Hex for hexadecimal representation (common in debugging). Choose Alphanumeric for human-readable tokens without special characters. Base64URL provides the best balance of compactness and compatibility.

[STEP 1] Generate & Copy Tokens

Click EXECUTE GENERATION to create bearer tokens with CSPRNG security. Each token displays with a Copy button for easy clipboard access. Tokens show their byte length, entropy bits, and strength assessment (weak/fair/good/strong/very_strong). All tokens use PHP's random_bytes for cryptographic randomness.

[STEP 1] Use in API Authentication

Copy tokens for API testing with "Authorization: Bearer " headers in Postman, cURL, or HTTP clients. Store tokens securely server-side associated with user permissions. Implement token validation by checking the token exists in your database and hasn't expired. Use HTTPS to protect tokens in transit.

Bearer Token Best Practices

  • _ HTTPS Only - Always transmit bearer tokens over HTTPS/TLS. Tokens sent over unencrypted HTTP can be intercepted via man-in-the-middle attacks. Never embed tokens in URLs (visible in browser history, server logs, and referrer headers). Use Authorization headers exclusively.
  • _ Sufficient Entropy - Use minimum 128 bits (16 bytes) of entropy for bearer tokens. OAuth 2.0 recommends 256 bits (32 bytes). Higher entropy makes tokens resistant to brute-force guessing. Our generator uses CSPRNG (random_bytes) ensuring unpredictability and cryptographic security.
  • _ Short Token Lifetimes - Set expiration times for bearer tokens (1 hour typical for access tokens). Implement refresh tokens for longer sessions. Store expiration timestamps server-side and validate on each request. Expired tokens should be rejected immediately. Short lifetimes limit exposure if tokens are compromised.
  • _ Secure Storage - Store bearer tokens securely server-side (database with encryption at rest). Never store tokens in client-side JavaScript localStorage (vulnerable to XSS). Use httpOnly cookies for web applications. Associate tokens with user IDs, permissions, and expiration times. Hash tokens before storage for additional security.
  • _ Token Revocation - Implement token revocation mechanisms. Maintain a database of active tokens that can be invalidated immediately. Check token validity on every API request against your authorization server. Support token revocation endpoints for user logout and security incidents.
  • _ Rate Limiting - Apply rate limiting to token-authenticated endpoints. Detect and block suspicious patterns (multiple failed attempts, unusual request volumes). Log token usage for security auditing. Implement account lockout after repeated authentication failures with invalid tokens.

Technical Implementation

Our bearer token generator uses PHP's random_bytes (CSPRNG) ensuring cryptographic randomness and unpredictability:

// Bearer Token Generation Algorithm (OAuth 2.0)
Algorithm: Cryptographically Secure Random Token Generation

// Step 1: Generate Random Bytes
byte_length = 32 (configurable: 16-128 bytes)
random_bytes = random_bytes(byte_length) // PHP CSPRNG
// Example: 32 bytes = 256 bits of entropy

// Step 2: Encode Based on Format
if (format == "base64url") then:
  // OAuth 2.0 standard (RFC 4648 Section 5)
  token = base64_encode(random_bytes)
  token = strtr(token, '+/', '-_') // URL-safe chars
  token = rtrim(token, '=') // Remove padding
  // Example: yH3kT9mN5pQ2xR7jL4wV6sZ8aB1cD0eF

else if (format == "base64") then:
  token = base64_encode(random_bytes)
  // Example: yH3kT9mN5pQ2xR7+jL4wV/6sZ8aB1c==

else if (format == "hex") then:
  token = bin2hex(random_bytes)
  // Example: c87de4...93f (64 hex chars for 32 bytes)

else if (format == "alphanumeric") then:
  charset = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
  token = ''
  for i = 0 to (byte_length * 2) do:
    token += charset[random_int(0, 61)]

// Step 3: Calculate Metadata
entropy_bits = byte_length * 8 // 32 bytes = 256 bits
strength = assess_strength(entropy_bits)

// Usage in HTTP:
// Authorization: Bearer yH3kT9mN5pQ2xR7jL4wV6sZ8aB1cD0eF

API Access for Developers

Generate bearer tokens programmatically using our free REST API. Specify count, byte length, and encoding format for automated OAuth 2.0 testing and CI/CD pipelines.
GET https://generate-random.org/api/v1/generate/bearer-tokens?count=10&length=32&format=base64url
VIEW FULL API DOCUMENTATION →

Frequently Asked Questions

What is the difference between bearer tokens and JWT tokens?

Bearer tokens are simple random strings used as access tokens in OAuth 2.0, with the authorization server maintaining all token metadata (user ID, permissions, expiration) server-side. JWTs (JSON Web Tokens) encode claims and user data directly in the token with cryptographic signatures for verification. Bearer tokens are simpler and allow immediate revocation but require database lookups. JWTs are stateless enabling horizontal scaling but cannot be revoked until expiration. Choose bearer tokens for OAuth 2.0 implementations with centralized authorization servers, JWTs for distributed microservices requiring stateless authentication.

Can I use these tokens in production applications?

These tokens are cryptographically secure using PHP's random_bytes (CSPRNG), but they are intended for testing, development, and educational purposes only. Production systems should generate bearer tokens server-side with proper storage, expiration tracking, and revocation mechanisms. Store tokens hashed in your database associated with user IDs and permissions. Implement token expiration checking and revocation endpoints. Never use client-side generated tokens for production authentication.

How do I validate a bearer token in my API?

Bearer token validation involves: (1) Extract token from Authorization header ("Bearer "), (2) Query your database for the token (use hashed lookup for security), (3) Check token exists and hasn't been revoked, (4) Verify expiration timestamp hasn't passed, (5) Retrieve associated user ID and permissions, (6) Authorize the requested action based on permissions. Return 401 Unauthorized for missing/invalid tokens, 403 Forbidden for insufficient permissions. Always use constant-time comparison when checking tokens to prevent timing attacks.

What byte length should I use for bearer tokens?

OAuth 2.0 recommends minimum 128 bits (16 bytes) of entropy. For most applications, 256 bits (32 bytes) provides excellent security balancing token length with brute-force resistance. High-security applications should use 512 bits (64 bytes). The entropy (bits = bytes × 8) determines difficulty of guessing: 128 bits = 3.4×10³⁸ possibilities, 256 bits = 1.2×10⁷⁷ possibilities. Use Base64URL encoding for compact representation. Longer tokens provide more security but result in larger HTTP headers (typically not a concern until 128+ bytes).

How long should bearer tokens remain valid?

OAuth 2.0 access tokens typically expire in 1 hour (3600 seconds) balancing security and user experience. Shorter expirations (15-30 minutes) provide better security for sensitive applications. Longer expirations (24 hours) reduce token refresh frequency for less sensitive APIs. Always implement refresh tokens for seamless re-authentication without requiring user credentials. Store expiration timestamps server-side and reject expired tokens. Consider token rotation strategies where tokens are refreshed before expiration for long-running sessions.

Should I store bearer tokens in localStorage or cookies?

Never use localStorage for bearer tokens - it's vulnerable to XSS (cross-site scripting) attacks where malicious JavaScript can steal tokens. Use httpOnly cookies which are inaccessible to JavaScript, providing XSS protection. Set Secure flag (HTTPS only) and SameSite=Strict or Lax to prevent CSRF attacks. For mobile/native apps, use secure platform storage (iOS Keychain, Android Keystore). For API clients, store tokens in memory or encrypted configuration files. Always transmit tokens over HTTPS to prevent interception.

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APA Style:
Generate-Random.org. (2025). Bearer Token Generator. Retrieved from https://generate-random.org/bearer-tokens
Web Citation:
Bearer Token Generator - Generate-Random.org (https://generate-random.org/bearer-tokens)