0X00000A8F

Fix 0X00000A8F Password Too Long Error on Windows

Windows Errors Intermediate 👁 6 views 📅 Jun 10, 2026

Windows says your password's too long at 0X00000A8F. It's almost always a registry limit issue. Here's the fix.

Quick Answer (for the impatient)

Open Regedit, go to HKLM\SYSTEM\CurrentControlSet\Control\ProductOptions, create or modify a DWORD named MaximumPasswordLength with value 256 (decimal), then reboot. That's it.

Why This Happens

This error pops up when Windows enforces a hidden maximum password length that's lower than what you're typing. It's not your domain policy or local security settings — it's buried in the registry. I've seen this most often on Windows 10 1809 and 21H2 builds, especially after a botched update or when someone manually tweaked ProductOptions to lock down passwords. The default limit is 256 characters, but some third-party software or a GPO override can drop it to 127 or even 64. The error code 0X00000A8F itself translates to STATUS_PASSWORD_TOO_LONG, and Windows throws it at logon, password change prompts, or when IT pushes a new password via script. The culprit here is almost always the MaximumPasswordLength value in ProductOptions — not Active Directory, not local user management, not the password filter DLLs.

Step-by-Step Fix

  1. Open Regedit as Admin — hit Win+R, type regedit, right-click and run as administrator. Don't skip this — a standard user can't edit ProductOptions.
  2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ProductOptions. If you don't see the ProductOptions key, right-click Control, select New > Key, and name it ProductOptions.
  3. Check for MaximumPasswordLength — look in the right pane for a DWORD (32-bit) value named MaximumPasswordLength. If it's there, double-click it. If not, right-click empty space, New > DWORD (32-bit), name it MaximumPasswordLength.
  4. Set the value to 256 (decimal) — make sure base is set to Decimal, not Hexadecimal. Type 256 and click OK. This matches the default Windows maximum. Don't go higher — Windows has a hard cap at 256 for NTLM and Kerberos.
  5. Reboot — this registry key gets read at boot time. A restart is mandatory. No workaround.
  6. Test — try logging in or changing your password again. The error should be gone.

Alternative Fixes (if the registry fix doesn't work)

1. Check Group Policy

If you're on a domain, a GPO might be overriding the registry. Run gpresult /h gp.html from an admin command prompt, open the HTML file, and search for MaximumPasswordLength or Password Policy. If a GPO sets it lower than 256, talk to your domain admin — don't override it locally. They'll need to adjust the GPO.

2. Verify Local Security Policy

Open secpol.msc and go to Account Policies > Password Policy. The Maximum password length setting there is separate from the registry key. If it's set to something like 16 or 32, raise it to 256. But honestly, I've never seen this fix the 0X00000A8F error alone — it's always the registry key.

3. Use NET USER to Force a Password Change

Sometimes the account itself is corrupted. From an admin command prompt, run net user username * (replace username). It'll prompt you to enter a new password. If the registry fix is done, this should work. If it still fails, the account profile is likely hosed — try a local user profile reset.

Prevention Tips

  • Never manually edit ProductOptions unless you know exactly what you're doing. It's a system-level key that also controls product type (Workstation vs Server). Messing it up can break activation.
  • Keep Windows updated — the bug that causes a missing MaximumPasswordLength key is patched in later builds. On Windows 10 22H2 and 11 22H2+, I haven't seen this error at all.
  • If you deploy custom password filters (like passfilt.dll), test them against 256-character passwords. Some third-party filters enforce their own lower limits that trigger this error.
  • Audit your GPOs regularly — a rogue policy can silently insert a lower MaximumPasswordLength. Use the Group Policy Management Console to check all password-related policies.
One more thing: if you're using a Microsoft Account (MSA) instead of a local account, this error is rare but possible. The fix is the same — registry key. But I've only seen it once in 14 years, so don't chase that rabbit unless you've ruled out everything else.

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