api-ms-win-crt-runtime-l1-1-0.dll Is Missing? Install the Universal C Runtime

A program won’t launch because “api-ms-win-crt-runtime-l1-1-0.dll is missing from your computer” (you may also see api-ms-win-crt-heap-, -string-, or other api-ms-win-crt-* names).

Why: The api-ms-win-crt-* DLLs and ucrtbase.dll are the Universal C Runtime (UCRT). Windows 10 and 11 include the UCRT natively, so on those systems this error usually means the runtime is missing or damaged — typically fixed by installing the Visual C++ Redistributable (which carries the UCRT) and making sure Windows is fully updated. On older Windows, the UCRT is delivered as a separate update (KB2999226).

Fix 1: Install the Visual C++ Redistributable

The Visual C++ Redistributable installs the Universal C Runtime files the app needs:

• x64: https://aka.ms/vc14/vc_redist.x64.exe
• x86: https://aka.ms/vc14/vc_redist.x86.exe

1. On 64-bit Windows, install both packages (32-bit apps need the x86 one).
2. Run each .exe, click Install, then reboot and retry the app.

Fix 2: Update Windows

On Windows 10 and 11 the UCRT is serviced through Windows Update, so a fully patched system has it:

1. Settings → Windows Update → Check for updates.
2. Install everything offered (including optional/quality updates), reboot, and check for updates again until it’s clean.

Fix 3: Older Windows — install the UCRT update (KB2999226)

If you’re on Windows 7/8/8.1 or Server 2008 R2/2012/2012 R2, the UCRT isn’t built in. Microsoft delivers it as the Update for Universal C Runtime in Windows (KB2999226) through Windows Update. Run Windows Update and install it (it’s a Recommended update), or grab the matching architecture/version package from the Microsoft support article below.

Fix 4: Repair system files if Windows itself is damaged

If updates are current but the DLL is still reported missing, repair Windows components. In an admin Command Prompt:

DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Run DISM first, then SFC, then reboot.

FAQ

Can I just copy api-ms-win-crt-runtime-l1-1-0.dll into the app folder? Don’t. A loose DLL from a download site is unsupported and risky. Install the redistributable / updates so the whole runtime is present and correct.

It names a different api-ms-win-crt DLL — same fix? Yes. All api-ms-win-crt-* files belong to the Universal C Runtime, so the same steps apply.

Sources: Microsoft Support — Update for Universal C Runtime in Windows (KB2999226) · Microsoft Learn — Latest supported Visual C++ Redistributable downloads