UseToolSuite UseToolSuite

RSA Key Pair Generator

Generate RSA public/private key pairs in your browser with the Web Crypto API. Keys are output in PEM format and never leave your device.

100% Client-Side Works Offline
Security reminder: Never share your private key. This key was generated entirely in your browser and was never transmitted to any server.

What is RSA Key Pair Generator?

RSA Key Pair Generator creates asymmetric cryptographic key pairs directly in your browser using the Web Crypto API. The tool generates mathematically linked public and private keys in PEM format, the most widely used format compatible with OpenSSL, SSH, JWT libraries, and virtually all cryptographic tools. Unlike server-based generators, this tool runs 100% client-side — your keys are generated on your device and never transmitted to any server, providing the highest possible level of trust and security.

When to use it?

Use this tool when you need RSA keys for SSL/TLS certificate generation, JWT token signing, SSH key setup, API authentication, encrypted communication between services, or any application requiring public-key cryptography. It is ideal for development and testing environments where you need quick key generation without installing OpenSSL or other command-line tools.

Common use cases

Security engineers and developers use RSA Key Pair Generator to create signing keys for JWT authentication, generate TLS certificate key pairs for development servers, produce SSH key pairs for server access, create keys for encrypted data exchange between microservices, set up webhook signature verification, and build proof-of-concept security implementations. The 2048-bit default is suitable for most applications, while 4096-bit keys provide a higher security margin for long-lived production keys.

What a key pair is

RSA is asymmetric cryptography: you generate a mathematically linked public and private key. The public key can be shared freely — others use it to encrypt data to you or to verify your signatures. The private key stays secret — you use it to decrypt or to sign. The security rests on the fact that deriving the private key from the public one requires factoring an enormous number, which is computationally infeasible. This tool generates the pair using the browser’s Web Crypto API, backed by the OS’s cryptographically secure RNG — the same randomness source production tools rely on.

Where these keys are used

UseRole of the keys
TLS/SSL certificatesServer identity + key exchange
SSH authenticationProve identity to a server (Ed25519 preferred)
JWT signing (RS256)Sign tokens with private, verify with public
Code/document signingAuthenticity + integrity

Formats and compatibility

Keys are output in PEM — the Base64 text format wrapped in -----BEGIN…----- headers, the most portable representation. Specifically, this tool emits SPKI for the public key and PKCS#8 for the private key, which modern OpenSSL, SSH (7.8+), and JWT libraries accept directly. If an older app rejects the key, it may expect the legacy PKCS#1 format (BEGIN RSA PRIVATE KEY); convert with openssl rsa -in key.pem -traditional. For SSH’s OpenSSH public-key format, run ssh-keygen -i -m PKCS8 -f public.pem.

Guard the private key

The entire security model collapses if the private key leaks — anyone holding it can impersonate you and decrypt your data. Never paste a private key into untrusted sites, commit it to a repo, or send it over chat/email. This generator runs entirely in your browser (verify by going offline — it still works), so keys are created locally and never transmitted. For development and learning that’s ideal; for high-value production keys, generate them in a controlled environment with proper key management and storage. The Bcrypt and HMAC tools cover the symmetric side of crypto.

RSA Key Pair Generator Powered by UseToolSuite — free browser tools

RSA Key Pair Generator creates what you need on the spot — no account, no sign-up, no server round-trip. It's one of the free Generator Tools on UseToolSuite.

Last updated

How helpful was this tool?

Click to rate

Embed this tool on your site

Paste this snippet into any HTML page or blog post to embed a live, fully working copy of RSA Key Pair Generator. Free for any use.

Key Concepts

RSA (Rivest-Shamir-Adleman)

One of the first and most widely used public-key cryptographic algorithms. RSA is based on the mathematical difficulty of factoring the product of two large prime numbers. It enables asymmetric encryption (encrypt with public key, decrypt with private key) and digital signatures (sign with private key, verify with public key). Common applications include SSL/TLS certificates, SSH authentication, and JWT signing.

PEM Format

A Base64-encoded text format for storing cryptographic keys and certificates, enclosed between header and footer lines (e.g., -----BEGIN PUBLIC KEY----- and -----END PUBLIC KEY-----). PEM stands for Privacy-Enhanced Mail and is the most common format for exchanging keys. It is human-readable, easy to copy-paste, and supported by virtually all cryptographic tools.

Key Pair (Public/Private)

A mathematically linked pair of cryptographic keys used in asymmetric cryptography. The public key can be freely shared and is used to encrypt data or verify signatures. The private key must be kept secret and is used to decrypt data or create signatures. The security of the system relies on the computational infeasibility of deriving the private key from the public key.

CSPRNG (Cryptographically Secure Pseudo-Random Number Generator)

A random number generator that produces output suitable for use in cryptographic applications. Unlike standard Math.random(), a CSPRNG (like the one backing Web Crypto API) guarantees that its output is unpredictable even to an adversary with knowledge of previous outputs. Operating systems provide CSPRNGs through interfaces like /dev/urandom (Linux) and CryptGenRandom (Windows).

Frequently Asked Questions

Are the keys generated securely?

Yes. The generator uses the Web Crypto API (window.crypto.subtle.generateKey), which is a browser-native cryptographic API that provides cryptographically secure key generation. The randomness source is the operating system CSPRNG (Cryptographically Secure Pseudo-Random Number Generator), the same source used by OpenSSL and other security-critical applications.

Do the generated keys ever leave my browser?

No. The entire key generation process runs locally in your browser using JavaScript and the Web Crypto API. No data is sent to any server — there are no API calls, no uploads, and no analytics on generated keys. You can verify this by disconnecting from the internet and using the tool offline.

What key sizes are supported?

The tool supports RSA key sizes of 1024, 2048, and 4096 bits. 2048 bits is the current industry standard minimum for secure communications. 4096 bits provides a higher security margin and is recommended for long-lived keys. 1024 bits is provided for legacy compatibility but is considered insecure for production use.

In what format are the keys output?

Keys are output in PEM (Privacy-Enhanced Mail) format, the most widely used format for RSA keys. The public key uses SPKI (Subject Public Key Info) format and the private key uses PKCS#8 format. These formats are compatible with OpenSSL, SSH, JWT libraries, and most cryptographic tools and libraries.

Can I use these keys for SSH authentication?

The generated keys are in standard PEM format (PKCS#8 for private, SPKI for public). For SSH, you would need to convert the public key to OpenSSH format using a command like `ssh-keygen -i -m PKCS8 -f public.pem`. The private key in PKCS#8 PEM format is directly usable by modern OpenSSH versions (7.8+).

Should I use RSA or Ed25519 for SSH keys?

For SSH in 2026, prefer Ed25519 unless you need RSA for compatibility. Ed25519 keys are tiny (the public key is one short line), generate and verify much faster, and offer security comparable to a 3000+ bit RSA key — all while being less prone to implementation mistakes. Generate one with ssh-keygen -t ed25519. Reach for RSA only when a system you must connect to doesn't support Ed25519 (some older servers, legacy appliances, or certain enterprise/Java environments) — in which case use RSA at 3072 or 4096 bits. So the rule: Ed25519 by default for SSH; RSA 4096 as the compatibility fallback. This tool generates RSA (useful for JWT signing, TLS, and RSA-requiring systems); for SSH specifically, Ed25519 via ssh-keygen is the modern recommendation.

Should I generate a 2048-bit or 4096-bit RSA key?

2048-bit is the current industry-standard minimum and is considered secure for most uses through the near-to-medium term; 4096-bit roughly quadruples the work to generate and sign/verify but adds a larger security margin for long-lived keys. Practical guidance: use 2048 for general use and anything performance-sensitive (TLS handshakes, high-volume signing) where the speed difference matters; use 4096 for keys that must remain secure for many years (root CAs, long-term code-signing) or when a security policy mandates it. Avoid 1024-bit entirely — it's broken for any real security use and provided only for legacy interop. Note 4096-bit generation can take several seconds on mobile/older hardware, which is normal, not a hang.

Troubleshooting & Technical Tips

Key generation takes a long time with 4096-bit size

RSA key generation for 4096 bits requires significantly more computation than 2048 bits (roughly 8x more). On mobile devices or older hardware, this can take 5–15 seconds. The browser may appear unresponsive during generation — this is normal. If you need faster generation, use 2048-bit keys, which provide adequate security for most applications.

Web Crypto API not available error

The Web Crypto API requires a secure context (HTTPS or localhost). If you are accessing the tool over plain HTTP, the browser will not expose the crypto.subtle API. Access the tool via HTTPS to resolve this issue. All modern browsers (Chrome 37+, Firefox 34+, Safari 11+, Edge 12+) support the Web Crypto API.

Generated PEM key is not accepted by my application

Verify that your application expects the correct PEM format. This tool generates PKCS#8 for private keys and SPKI for public keys. Some older applications expect PKCS#1 format (headers: BEGIN RSA PRIVATE KEY / BEGIN RSA PUBLIC KEY). Use OpenSSL to convert between formats: `openssl rsa -in private.pem -out private_pkcs1.pem -traditional`.

Related Guides

Are Online Password Generators Safe? What Client-Side Really Means

Is a web password generator safe? It comes down to one thing: is the password created in your browser or on a server? How to tell, and why it matters.

Related Tools

Password Generator

Generator Tools

Hash Generator

Encoding & Decoding Tools

Bcrypt Generator & Verifier

Encoding & Decoding Tools