The error you may be seeing
The program can't start because ac1st19.dll is missing from your computer.
Try reinstalling the program to fix this problem.
You may instead see:
The code execution cannot proceed because ac1st19.dll was not found.
Reinstalling the program may fix this problem.
Or:
ac1st19.dll is either not designed to run on Windows
or it contains an error.
ac1st19.dll is an Autodesk AutoCAD component, not a Windows system DLL. The safest fix is to identify the AutoCAD or AutoCAD-based product that needs it, then repair or reinstall that exact installation.
Which fix applies to you
- AutoCAD stopped launching after a failed update or cleanup: use the built-in Autodesk repair option first.
- The DLL is missing from the AutoCAD installation folder: repair the product, then reinstall it if repair fails.
- The error appeared after antivirus activity: check Windows Security Protection history before reinstalling.
- The message also names
MSVCP140.dll,VCRUNTIME140.dll,mfc140u.dll, orapi-ms-win-crt-*.dll: repair the relevant Microsoft Visual C++ runtime. - The file exists but AutoCAD still reports it as missing: check its full path, signature, dependencies, and Event Viewer.
- The error began after replacing files manually: remove the mismatched files and restore the complete Autodesk installation.
- Windows itself reports several damaged-system errors: run DISM and SFC after addressing the Autodesk installation.
- The failure is a graphics crash rather than a missing-DLL message: investigate drivers only after the application installation is known to be intact.
What ac1st19.dll is and where it belongs
The name is associated with Autodesk’s AutoCAD release family. Autodesk documentation for AutoCAD 2014 places Ac1st19.dll in the product installation directory and identifies a specific hotfix build as 19.1.108.27. AutoCAD 2014 is documented as release 19.1, while AutoCAD 2013 is release 19.0.
As an Amazon Associate I earn from qualifying purchases.
That does not mean every copy of ac1st19.dll should have that version. AutoCAD, AutoCAD LT, and AutoCAD-based vertical products can use related components, and the correct file depends on the installed product, release, architecture, service pack, and hotfix state.
The file should normally be beside the Autodesk executable in the application directory, not in:
C:WindowsSystem32
or:
C:WindowsSysWOW64
Do not use a generic DLL download site. A downloaded file can contain malware, belong to a different AutoCAD release, use the wrong architecture, or leave the original installation damage unresolved.
1. Confirm which Autodesk product is failing
Before repairing anything, record the exact program named in the error window. It may be AutoCAD, AutoCAD LT, or an Autodesk-based vertical product.
Then check the installed product:
- Press
Win + R. - Type
appwiz.cpl. - Press Enter.
- Look for the Autodesk product and its release in Programs and Features.
- Write down the full product name and release.
You can also search the normal Autodesk installation area from an elevated or ordinary Command Prompt:
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
where /r "C:Program FilesAutodesk" ac1st19.dll
If the result points to an Autodesk product folder, note the complete path. If there is no result, do not immediately download the file. The installation may be incomplete, or the product may be installed elsewhere.
A file’s presence is not proof that it is the right file. Check whether it is inside the folder belonging to the failing AutoCAD executable. A copy in a temporary folder, an old backup, or another Autodesk release should not be substituted.
2. Repair AutoCAD from Windows
For older AutoCAD releases, Autodesk’s documented repair route uses Control Panel.
- Close AutoCAD and other Autodesk programs.
- Press
Win + R. - Enter
appwiz.cpl, then press Enter. - Select the affected AutoCAD product.
- Choose Uninstall/Change, Change, or Modify.
- Select Repair or Reinstall.
- Choose Repair.
- Follow the installer prompts.
- Restart Windows when the repair completes.
- Launch the same AutoCAD product again.
The wording varies by release and installer. Do not remove the product when the repair option is available.
Rank #2
- One-Click Automatic Printing: Experience hassle-free 3D printing with the Adventurer 5M Series. Enjoy automatic bed leveling for flawless first layers, ensuring consistent adhesion and saving time with no manual adjustments required.
- 12X Ultra Fast Printing: Featuring a CoreXY structure with 600mm/s travel speed and 20000mm/s² acceleration, the AD5M maximizes efficiency, reduces production cycles, and ensures high precision, making it ideal for rapid prototyping and mass production.
- Smart and Efficient Design: Quick 3-second nozzle changes, a high-flow 32mm³/s nozzle, and fast 35-second warm-up to 200°C deliver stable high-speed printing. Its dual-sided PEI platform and versatile options provide easy removal and adaptability for various creative projects.
- Superior Print Quality & Adaptability: Combines a 280°C direct drive extruder with dual-fan cooling and vibration compensation. Includes a standard 0.4mm nozzle and accepts optional sizes from 0.25mm to 0.8mm to fit various printing needs.
- Real-Time App Monitoring: Monitor print progress, adjust settings, and receive instant status alerts remotely with the Flash Studio. Smart mobile control ensures a seamless, effortless printing experience anytime, anywhere.
A successful repair restores the application files to the product’s own directory and allows AutoCAD to open normally. If the same message remains, restart once more and test from the original shortcut rather than from a copied executable.
If repair fails, or if the installer reports that source files are unavailable, continue to a clean reinstall.
3. Reinstall the exact Autodesk product
A clean reinstall is appropriate when the installation was interrupted, files were manually deleted, a service pack was only partly applied, or the repair process cannot restore the files.
Before removing the product, save custom templates, profiles, plot styles, and other work-specific settings if they are important to you. Do not delete Autodesk folders manually as the first step.
Recommended Free Tools
- Open Control Panel > Programs and Features.
- Select the affected Autodesk product.
- Choose Uninstall/Change.
- Remove the product using its Autodesk uninstaller.
- Restart Windows.
- Use Autodesk’s documented clean-uninstall procedure for the affected release if remnants prevent installation.
- Restart again if requested.
- Sign in to your Autodesk account or use the original official Autodesk installer.
- Download the same product and release that created the error.
- Match the installer to the computer’s supported architecture.
- Install the product completely.
- Apply only service packs or hotfixes intended for that product and release.
- Restart Windows and test AutoCAD.
Do not replace one file from a different release after reinstalling. For example, Autodesk’s 2014 hotfix documentation lists separate 32-bit and 64-bit packages for AutoCAD and AutoCAD LT. Its 19.1.108.27 file version applies to that documented hotfix, not automatically to every AutoCAD installation.
4. Check architecture and file matching
Mixing files is a common way to turn one missing-DLL error into several load failures.
Check all of the following:
- The exact Autodesk product, not merely “AutoCAD.”
- The product release.
- Whether the application is 32-bit or 64-bit.
- Whether a service pack or hotfix is installed.
- Whether
ac1st19.dllcame from the same installation package. - Whether antivirus restored the file to its original folder.
Do not choose the “newest” DLL by filename or file size. The known metadata sometimes associated with this filename is not a universal specification, and a reported 32-bit version or size should not be used to select a replacement for every system.
If you have a legitimate Autodesk hotfix package, replace files only when its product, release, architecture, and installation instructions match exactly. In most cases, repairing or reinstalling the complete product is safer than replacing one file.
Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errors5. Check antivirus quarantine
If AutoCAD worked until a security scan or update, the file may have been quarantined.
- Open Windows Security.
- Select Virus & threat protection.
- Choose Protection history.
- Look for an event involving
ac1st19.dll. - Confirm that the original path is inside the expected Autodesk installation directory.
- Do not restore a file from an unknown or temporary location.
- If the file is clearly part of the genuine Autodesk installation, follow your organization’s security policy before choosing Restore or Allow on device.
- Repair AutoCAD afterward if the restored file is damaged or incomplete.
The absence of a quarantine event does not prove antivirus was unrelated. Security software from another vendor may have its own history and policy controls. Do not disable protection broadly just to make AutoCAD launch.
6. Repair Microsoft Visual C++ only when its files are named
Visual C++ is not a replacement for ac1st19.dll. It becomes relevant when the error also names files such as:
MSVCP140.dllVCRUNTIME140.dllmfc140u.dllapi-ms-win-crt-*.dll
Use Microsoft’s official latest supported Visual C++ Redistributable downloads.
- Download the Microsoft package that matches the application architecture.
- Use
vc_redist.x86.exefor a 32-bit application. - Use
vc_redist.x64.exefor a 64-bit application. - Run the installer.
- Choose Repair if offered, or install the package.
- Restart Windows.
- Test AutoCAD again.
Multiple Visual C++ redistributable versions can coexist. Do not remove every runtime from Installed apps unless a specific Autodesk repair instruction requires it.
7. Repair Windows components when Windows shows broader damage
DISM and SFC repair Windows component problems. They normally will not restore an Autodesk application DLL, so use them when Windows has other corruption symptoms or Autodesk installation repeatedly fails.
Rank #4
Open Terminal (Admin) or Command Prompt (Admin):
- Right-click Start.
- Select Terminal (Admin) or Command Prompt (Admin).
- Run:
DISM.exe /Online /Cleanup-image /Restorehealth
- Wait for it to finish.
- Then run:
sfc /scannow
- Restart Windows.
- Test AutoCAD.
Microsoft recommends running DISM before SFC. If either command reports that it could not complete, record the exact message and repair the Autodesk installation separately.
Manually hunting through Windows components and repeating SFC or DISM without knowing what changed can waste time. Outbyte PC Repair provides a free scan that shows what it identifies, while repair is handled by the full version; it is optional, and reinstalling the Autodesk product remains the definitive fix for a missing application DLL.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchPC Slower Than It Used to Be?
A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 118. Do not register or copy this DLL
regsvr32 is not a general DLL repair command. It is intended for libraries that provide a registration entry point such as DllRegisterServer. There is no Autodesk instruction establishing that ac1st19.dll should be registered this way.
Do not run:
regsvr32 ac1st19.dll
Do not copy it into System32 or SysWOW64. Windows searches the application directory before system directories, and putting a private Autodesk library into a system folder can create version conflicts and security problems.
If the file exists in the correct Autodesk folder but Windows still reports it as missing, a dependent DLL may be missing. Check Event Viewer:
- Press
Win + R. - Enter
eventvwr.msc. - Open Windows Logs > Application.
- Look for an error at the time AutoCAD failed.
- Record the application name, faulting module, and any additional runtime DLL named there.
Then repair the complete Autodesk installation rather than copying individual dependencies.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →9. Update drivers only for graphics-related failures
A direct ac1st19.dll missing message is primarily an application-installation problem. Device Manager and graphics-driver updates are lower-priority steps unless the application opens and then crashes, reports an access violation, or shows a graphics-related load failure.
If that describes your case:
- Right-click Start.
- Select Device Manager.
- Expand Display adapters.
- Right-click the graphics adapter.
- Choose Update driver.
- Select Search automatically for drivers.
- Restart Windows and test AutoCAD.
For a more complete manufacturer-supported driver update, use the computer or graphics adapter manufacturer’s official support channel. Outbyte Driver Updater provides a free scan showing which drivers it identifies, while driver installation is handled by the full version; it is optional and does not replace repairing AutoCAD.
Do not use Device Manager to chase a missing ac1st19.dll unless the evidence points to a graphics or device problem.
Best Value
- Heavy-Duty Wobble-Free Base: Thick steel tubing and solid 39.3"×23.6" MDF top hold heavy 3D printers stably, eliminating vibrations for smooth, precise printing.Patent pending
- Dual-Tier 56 Spool Storage: Two slotted lower metal shelves securely hold up to 56 filament rolls, preventing rolling and keeping materials tidy.The adjustable spacing accommodates supplies of any size.
- Compact 3-Tier Space Saver: Vertical multi-layer layout frees up cluttered desktops, neatly organizing printers, filaments, and tools in one spot.
- Adjustable Leveling Feet: 4 rotatable bottom pads easily balance the stand on uneven floors while protecting wood and tile from scratches.
- Quick 25-Minute Assembly: Straightforward modular design with included tools and clear guide ensures fast, hassle-free setup by a single person.
10. Use System Restore only as a last resort
System Restore can help when the failure clearly began after an installation, update, or configuration change and other repairs have failed.
Free tools Windows power users keep installed
One-click scans. No signup required.
- Press
Win + R. - Type:
rstrui.exe
- Press Enter.
- Choose a restore point from before the failure.
- Review the affected programs.
- Start the restore and allow Windows to restart.
System Restore is not a substitute for reinstalling AutoCAD. Avoid it when you cannot identify a suitable restore point or when restoring would remove important recent software changes.
FAQ
Is ac1st19.dll a Windows file?
No evidence supports treating it as a Windows system DLL. Autodesk documentation places it with AutoCAD software.
Can I download ac1st19.dll by itself?
Do not use random DLL download websites. Obtain the file through repair or reinstallation of the matching Autodesk product and its official installer.
Does AutoCAD 2014 always need version 19.1.108.27?
No. That version is identified in a specific Autodesk hotfix document. It is not proof that every AutoCAD installation should use that build.
Why does Windows say the DLL is missing when the file is present?
A dependent library may be missing, the file may be in the wrong folder, or the copy may be damaged or mismatched. Check Event Viewer and repair the installation.
Should I use regsvr32?
No. This is not established as a self-registering component, and regsvr32 does not restore damaged application files.
What information should I provide for further help?
Include the exact AutoCAD product and release, Windows version, complete error text, full DLL path, file version and architecture if available, whether antivirus quarantined it, and relevant Event Viewer details.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →
