What the tool is for
The tool generates time-based one-time passwords for authenticator-style 2FA and MFA setup keys. It accepts Base32 secrets and otpauth:// TOTP URIs, including common options such as algorithm, digits, and period.
About this 2FA TOTP tool
This page describes the purpose, supported workflows, limitations, and relationship boundaries of the local authenticator code generator.
Who it helps
It is useful when a service shows a manual setup key instead of a QR code, when testing a TOTP integration, when checking account recovery settings, or when temporarily managing multiple setup keys.
Compatibility and affiliation
This independent utility is published by ChatGPT UK at chatgpt.org.uk. The generator is compatible with standard TOTP setup keys used by many authenticator apps, but it is not affiliated with Google, Microsoft, Cloudflare, OpenAI, or any account provider mentioned on the site.
Important limits
The tool cannot generate SMS codes, email codes, recovery codes, push approvals, passkeys, hardware security key responses, or any code without the shared setup secret from the account's 2FA setup page.
How calculation accuracy is checked
The implementation is checked against all 18 expected outputs in RFC 6238 Appendix B: six fixed timestamps across SHA-1, SHA-256, and SHA-512. The TOTP test-vector page and machine-readable JSON expose the same public inputs and outputs for independent comparison. These checks verify algorithm output; they do not audit a user's device, browser, account, or secret storage.
Standards and references
- RFC 6238: TOTP: Time-Based One-Time Password Algorithm
- RFC 4226: HOTP: An HMAC-Based One-Time Password Algorithm
- Google Authenticator Key URI Format
FAQ
Is this a replacement for an authenticator app?
It can generate compatible TOTP codes in the browser, but important long-term secrets are usually better stored in a trusted authenticator app or password manager.
Does it support multiple generators?
Yes. The main page starts with one generator, and you can add more generators for separate 2FA or MFA setup keys.
What information do I need to generate a code?
You need the shared TOTP setup secret, usually shown as a Base32 manual setup key or embedded in an otpauth:// URI. Without that secret, the correct authenticator code cannot be calculated.
How is the TOTP calculation checked?
Automated checks compare SHA-1, SHA-256, and SHA-512 results with all 18 expected RFC 6238 Appendix B outputs. The public test-vector page and JSON dataset let developers repeat the comparison independently.