Stop Firefox Autocomplete from Revealing Sensitive Info — A Step-by-Step Guide
1. What the risk is
Autocomplete stores form entries (names, emails, addresses, credit-card-related fields) in the browser and suggests them later. Misconfigured sites, shared devices, or malicious scripts can expose those suggestions to others.
2. Quick precautions (one-line actions)
- Use a master browser profile per person on shared devices.
- Disable autocomplete for sensitive fields.
- Clear form history regularly.
- Use a password manager for credentials instead of Firefox’s autofill.
- Lock your profile with a strong OS account password.
3. Step-by-step: disable form autocomplete globally
- Open Firefox.
- In the address bar go to about:config and accept the risk.
- Search for:
- browser.formfill.enable — double-click to set to false (disables saved form data).
- Signon.autofillForms — double-click to set to false (disables password autofill).
- Restart Firefox.
4. Step-by-step: disable autocomplete on specific fields (site-side)
- As a site owner or developer, add autocomplete=“off” or a specific token (e.g., autocomplete=“new-password”) on sensitive input elements:
Note: Some browsers ignore autocomplete=“off” for login fields; prefer stronger UX patterns.
5. Clear existing saved form data
- Menu → Settings → Privacy & Security.
- Under History click Clear Recent History or Clear Data.
- Choose Form & Search History and clear.
6. Use a password manager and secure autofill alternatives
- Use a dedicated password manager (1Password, Bitwarden, KeePassXC) to store credentials and payment info; these typically have more granular control and encryption.
- Disable Firefox’s built-in forms autofill if using an external manager.
7. Protect on shared devices
- Create separate OS accounts or separate Firefox profiles (Click menu → Profiles or run firefox -P).
- Use a temporary browsing mode (Private Window) for transactions you don’t want saved.
8. Advanced: encrypt profile or lock access
- On sensitive machines, encrypt the user profile folder or the entire disk (BitLocker, FileVault, LUKS).
- Use OS account passwords and automatic screen-lock policies.
9. Test that autocomplete is disabled
- Open a new profile or private window, visit a form, type part of a previously-saved value — suggestions should not appear.
- For developers: inspect page scripts to ensure no script reads autocomplete suggestions.
10. Maintenance best practices
- Periodically review saved form history and removed entries.
- Keep Firefox updated.
- Audit installed extensions; remove ones that request form or clipboard access unless necessary.