← Back to Blog

How to Load a LISP Routine in AutoCAD

LISP routines are plain text files with a .lsp extension. AutoCAD has had a built-in LISP interpreter since version 2.1 — which means almost any version you're running can execute them. The challenge is knowing how to get a file loaded and running.

Here are the four main ways to load a LISP file, from quickest to most permanent.

Method 1: Drag and Drop

The fastest way for a one-time load. Simply drag the .lsp file from Windows Explorer directly into the AutoCAD drawing window. AutoCAD will load and execute it immediately. Any commands defined in the file are now available for the rest of that session.

Downside: the routine is gone when you close and reopen AutoCAD.

Method 2: APPLOAD Command

Type APPLOAD at the command line and press Enter. A dialog box opens where you can browse to your .lsp file and click Load. There's also a "Startup Suite" section at the bottom — add your file there and it will load automatically every time AutoCAD starts.

Method 3: Load via the Command Line

You can load a LISP file programmatically using the load function directly at the AutoCAD command prompt:

(load "C:/Tools/MyRoutine.lsp")

Note that AutoCAD LISP paths use forward slashes, not backslashes. This is useful when you want to load a specific file quickly without opening a dialog.

Method 4: ACADDOC.LSP (Auto-load Every Drawing)

If you place a file named acaddoc.lsp in a folder that's on AutoCAD's support file search path, AutoCAD will load it automatically every time a drawing opens. This is the most powerful option for routines you use constantly.

1. Create a file named acaddoc.lsp
2. Add a load call for each routine you want: (load "C:/Tools/MyRoutine.lsp")
3. Place acaddoc.lsp in a trusted support path folder

Running a Command After Loading

Once a routine is loaded, any commands it defines are available at the command line. For example, if a routine defines a command called FIXLAYERS, simply type FIXLAYERS and press Enter to run it — exactly like a built-in AutoCAD command.

Troubleshooting

• File won't load: Check SECURELOAD — if set to 1 or 2, LISP files must be in a trusted path. Add your folder via TRUSTEDPATHS.
• Command not found after loading: The routine may have a syntax error. Check the command line for error messages when the file loads.
• Works in one drawing but not another: LISP loads are per-session unless you've set up auto-load via APPLOAD or acaddoc.lsp.