Program file
steamui.dll: part of the Steam client, or a file that should not be there?
steamui.dll is the SteamUI Dynamic Link Library, a large Valve file that the Steam client loads from its own install folder. Exactly one genuine copy exists on a PC with Steam, next to Steam.exe. Because the Steam client holds account logins, a steamui.dll anywhere else, or one changed by a third-party tool, is worth a careful look.
Prefer to check it yourself? The manual checks follow.
A steamui.dll in the root of the Steam install folder, by default C:\Program Files (x86)\Steam, reporting Valve Corporation and SteamUI Dynamic Link Library and signed by Valve, is the genuine client file. It is not a process of its own: it works inside Steam.exe, so Task Manager shows Steam, not the DLL.
Games never use this file. A steamui.dll in a game folder, in Downloads or in AppData was not put there by Steam, and a modified copy inside the Steam folder runs with access to the Steam account every time you sign in.
- Publisher
- Valve Corporation
- Description in the file
- SteamUI Dynamic Link Library
- Shipped by
- The Steam client for Windows only. No game ships or loads it
- Genuine folder
- The root of the Steam install folder, beside Steam.exe. By default C:\Program Files (x86)\Steam
- Size
- Several megabytes: about 10 MB to 16 MB across the Valve copies collected in a public DLL catalogue, all 32-bit builds
- Signed by
- Valve Corp. (check the signature; a file changed after Valve signed it fails the check)
- Runs as a process
- No. Steam.exe loads it when the client starts
- Changes with
- Every Steam client update, so its version number changes often
What steamui.dll does
Steam.exe on its own is a small starter. When you open Steam, it checks for client updates and then hands the work to its libraries, and steamui.dll is the one that carries the client itself: the sign-in, the Library, the store, the friends list and the download manager all run through it. That is why the file is so large for a DLL, and why Steam shows Failed to load steamui.dll and stops when the file is damaged, blocked or gone.
For security this makes steamui.dll different from the DLLs games ship. A game library touches one game; steamui.dll runs inside the program that keeps your Steam session, your saved login and your payment methods. Valve signs it and replaces it with every update. A copy that is not Valve's, or a genuine one that a third-party tool has patched, deserves more suspicion than a stray game file.
About .dll files. A .dll file is a library: it cannot run on its own and is loaded into a program's process. It does not appear in Task Manager under its own name; Process Explorer shows which process loaded it.
How to check a copy of steamui.dll
Four questions settle it: where the file is, what it says about itself, who signed it, and whether its size looks like a Valve build.
- Find every copy on the PC. There should be one result, in the Steam install folder. Any other path, such as a game folder, Downloads, Temp or AppData, is a file no program needs there.
Get-ChildItem -Path C:\ -Filter steamui.dll -Recurse -Force -ErrorAction SilentlyContinue | Select-Object FullName, Length, LastWriteTime - Read the company and description. Valve's file reports Valve Corporation and SteamUI Dynamic Link Library. Empty or different fields point to a file that is not Valve's. A careful fake can copy them, so do not stop here.
(Get-Item "C:\Program Files (x86)\Steam\steamui.dll").VersionInfo | Format-List CompanyName, FileDescription, FileVersion - Check the digital signature. Status Valid with Valve as the signer means the file is as Valve shipped it. NotSigned or HashMismatch means it was replaced or patched. This is the check that cannot be faked by copying text fields.
Get-AuthenticodeSignature "C:\Program Files (x86)\Steam\steamui.dll" | Format-List Status, SignerCertificate - Compare the size. The Valve builds in the catalogue are about 10 MB to 16 MB. The same catalogue also holds one copy of about 1.4 MB that reports no company and version 0.0.0.0: a file of that kind is not one of Valve's builds. Use the file check on this page for the checksum.
A valid Valve signature clears steamui.dll only. Tools that change the Steam client can work through other files in the Steam folder, so a clean steamui.dll does not prove the whole folder is untouched.
Check your steamui.dll
Choose the steamui.dll you are unsure about. Its SHA-256 and SHA-1 checksums are calculated in your browser and compared with the 7 versions of the file known from a public DLL catalogue.
The file stays on your computer. Nothing is uploaded: the checksum is computed locally.
Do you need steamui.dll?
If you use Steam, you need the copy next to Steam.exe: without it the client does not start. Any other copy has no job on the PC. What to do depends on where the file failed the checks.
- Keep the copy in the Steam folder. If it passed the checks, leave it alone. If the signature failed, do not try to swap the file by hand: Steam's own installer, run over the existing folder, replaces it with a signed copy and keeps the installed games.
- Remove third-party Steam client tools. Skins, patchers and unlockers that change the client are the usual reason for a modified steamui.dll. Uninstall them and delete what they added, then let Steam reinstall its own files.
- Delete copies outside the Steam folder. A steamui.dll in a game folder, Downloads, Temp or AppData is not used by Steam. Note its path, then delete it together with the package or game it came with.
- Run a Microsoft Defender full scan and the offline scan. Open Windows Security, Virus and threat protection, Scan options, and run a Full scan, then a Microsoft Defender Offline scan, which checks the PC before Windows starts.
Start-MpWDOScan - Secure the Steam account. If a modified or misplaced steamui.dll was found, assume the Steam session could have been read. From a clean device change the Steam password, sign out of all other devices in the account settings and check that Steam Guard is on.
Warning signs
| What you see | What it means |
|---|---|
| steamui.dll anywhere outside the Steam install folder | Steam never puts it there and no game loads it. Find out where it came from. |
| The signature check shows NotSigned or HashMismatch | The file in the Steam folder is not as Valve shipped it. |
| A copy of about 1 MB to 2 MB, or with no company name | Far from the size of Valve's builds. Treat it as unknown. |
| A steamui.dll inside a game you downloaded for free | Part of an unofficial package. Remove the game and scan. |
| Steam changed its look or features after a tool you installed | A client patcher is at work. Make sure you trust its source. |
| One copy, next to Steam.exe, signed by Valve | Normal. That is the genuine client file. |
Known versions of steamui.dll
A public DLL catalogue lists 7 versions of steamui.dll, from 0.0.0.0 to 5.97.91.35, by Valve Corporation. Its copies are uploaded by users and not verified, so a checksum match identifies the version, while the digital signature tells you whether the file is genuine. Even a genuine file clears only the file, not the folder: attackers ship genuine libraries next to a program they abuse, so where the copy sits still decides whether it is safe.
Every version with its checksums, and how to fix steamui.dll errors on uGetFix
Questions people ask
Is steamui.dll a virus?
No, the steamui.dll next to Steam.exe is part of Valve's Steam client and is signed by Valve. A security alert about it is worth reading closely, though: check the path in the alert and the signature of the file. A copy outside the Steam folder, or one that fails the signature check, is not Valve's file as shipped.
Why is steamui.dll so large?
Because it carries most of the Steam client. Steam.exe only starts the client and checks for updates; the window, the Library, the store and the downloads are handled by its libraries, steamui.dll among them. The Valve builds collected in a public DLL catalogue range from about 10 MB to 16 MB, so a small file of the same name is suspicious.
I found steamui.dll in a game folder. Is that a problem?
It is a file that should not be there. Games do not use steamui.dll; they ship steam_api.dll or steam_api64.dll instead. A steamui.dll beside a game's .exe came with an unofficial copy of the game or another package. Check its signature, and if the game did not come from a store you trust, remove the whole game and run a full scan.
Can a fake steamui.dll steal my Steam account?
A file loaded by Steam.exe runs inside the Steam client, which holds your signed-in session. A modified or replaced steamui.dll would therefore have the same reach as the client itself. That is why a failed signature check on this file is a reason to remove the tool that changed it, reinstall Steam and change the Steam password from a clean device.
Can I delete steamui.dll?
Deleting the copy in the Steam folder only stops Steam from starting; it comes back when you reinstall the client. Copies in other places can be deleted, since nothing needs them there. If you are not sure which is which, check the folder: the genuine one sits beside Steam.exe and nowhere else.
Why does the version of steamui.dll keep changing?
Steam updates its client often and replaces steamui.dll as part of each update, so the file version on your PC rarely stays the same for long. A changing version is normal. What should stay the same is the folder, the company name Valve Corporation and a valid Valve signature.
Sources
- Steam Support: Steam Client Troubleshooting
- Steam Support: Programs Which May Interfere with Steam
- MITRE ATT&CK T1574.001: Hijack Execution Flow: DLL
- Microsoft Learn: Get-AuthenticodeSignature
Version data read on Oct 17, 2026.
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