Firefox Password Manager — Complete Guide

In this tutorial, you'll learn about Firefox Password Manager. We cover key concepts, practical examples, and best practices.

Hook

You log into a site in Firefox, and the "Save password?" prompt does not appear. Or it appears, you click Save, but the password is not there when you return. Your Firefox password manager seems to be ignoring your credentials.

The Wrong Way

Setting signon.rememberSignons to false in about:config (or unchecking "Ask to save passwords") obviously disables the prompt, but some users toggle it off and on hoping to reset it — which does not fix the underlying issue.

# BAD: Toggling password saving off and on
# about:config → signon.rememberSignons → false → true

Password prompt: still missing for specific sites
Toggling did not affect the per-site exception

Per-site exceptions persist independently of the global setting.

The Right Way

Check per-site exceptions and the saved logins list.

# 1. Check if the site is in the "Never Save" list
# about:preferences#privacy → Saved Logins → "Never Save" tab

# 2. Remove the site from exceptions if present

# 3. Check if a password is already saved for this site
# about:logins → Search for the site

# 4. If the login exists but does not auto-fill, check the form selector
# The site may have changed its login form HTML
# Delete the old entry and save a new one

# 5. Reset the password manager if corrupted
# about:config → search and reset:
# signon.rememberSignons
# signon.autofillForms
# signon.storeWhenAutofill

# 6. Check primary password (master password) status
# about:preferences#privacy → "Use a Primary Password"
# If enabled and forgotten, passwords cannot be accessed

# 7. For Sync-related password issues:
# about:logins → Three dots → "Sync Logins" (force sync)

Passwords synced: 42 logins
Password prompt appears for new login ✓
Auto-fill works on saved sites ✓

Prevention

• Keep the Primary Password feature enabled for security.
• Do not add sites to the "Never Save" list unless intentional.
• Periodically review saved logins in about:logins and remove stale entries.
• Keep Firefox updated — password manager improvements are in every release.
• Use about:logins export feature for backup.

Common Mistakes with password manager

1. Using head and tail instead of pattern matching, causing runtime errors on empty lists
2. Forgetting that lazy evaluation defers computation until the value is forced, causing space leaks with unevaluated thunks
3. Using return to exit a function early instead of wrapping a pure value in the monad

These mistakes appear frequently in real-world FIREFOX code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

DodaTech — passwords that save when you need them.