Every file that starts with api-ms-win-crt - runtime-l1-1-0, string-l1-1-0, heap-l1-1-0, math-l1-1-0 and some forty siblings - belongs to one thing: the Universal C Runtime that modern programs share. When any of them is reported missing, the runtime as a whole is absent or damaged. Fix the runtime once and the entire family comes back together.
Fix it automatically
Outbyte PC Repair checks Windows for corrupted system files, registry problems and leftovers from removed programs - the kind of damage behind errors like this one. Useful when you would rather not run the steps below by hand - the check and the diagnosis are free, and nothing is changed until you decide.
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Run Windows Update until nothing is left (on Windows 7/8.1 the Universal C Runtime arrives as an update - KB2999226), then install both vc_redist.x64.exe and vc_redist.x86.exe from Microsoft's Visual C++ Redistributable page, and restart. Do not download the single DLL the message names - it is one of a set and a lone copy only moves the error to the next file.
Windows 10 and 11 ship with it, but Windows 7 and 8.1 received it through an update. A PC that skipped updates has no UCRT until something installs it.
A failed update, disk error or aggressive cleanup corrupted the shared runtime files - so a program that ran yesterday fails today.
The api-ms-win-crt files are a set of small forwarders into the real runtime. The message names whichever one a program touched first - the actual problem is always the set, not the single file.
Most installers add the Visual C++ Redistributable they need; when that step is skipped or fails silently, the program starts without its runtime.
sfc /scannow.DISM /Online /Cleanup-Image /RestoreHealth, then SFC again, then restart.Do not do this: Never download api-ms-win-crt-runtime-l1-1-0.dll - or any file from this family - as a single DLL from a download site. These files only work as a complete set; a lone copy moves the error to the next name, and such sites are a well-known malware channel. The official installers are free and restore all of them correctly.
No. All api-ms-win-crt files - runtime, string, heap, math, conv, locale and the rest - belong to the same Universal C Runtime and arrive together. Whatever variant the message names, the fix is the same: Windows Update plus the Visual C++ Redistributable.
The new program was built against the Universal C Runtime and your Windows - usually 7 or 8.1 - does not have it yet. Older Windows received the UCRT through an update, not with the system, so a PC that never updated shows the error the first time such a program starts.
No. These files work as a set of forwarders into the real runtime - copying one only moves the error to the next name in the family, and files from DLL download sites are unverified and a known malware channel. Install the runtime properly and all forty-plus files arrive together. Related reading: the VCRUNTIME140.dll guide covers the other half of the same runtime.
Outbyte PC Repair checks the system and shows what it found - then waits. Nothing is applied without your OK, and a restore point lets you undo changes.
Download Downloads Outbyte PC Repair for Windows. Free by-category trial included.