Emacs Slow or Freezing With Large Files

How to fix it

Try these in order — the most common fix is first.

1. 1. Enable so-long

   Copy steps
   1. Run M-x global-so-long-mode
   2. Add (global-so-long-mode 1) to your init file
   3. Emacs switches to a lightweight mode on files with very long lines
   Did this fix it? Yes No

2. 2. Open as plain text

   Copy steps
   1. Run M-x fundamental-mode in the buffer
   2. Or open the file with M-x find-file-literally
   Did this fix it? Yes No

3. 3. Check your packages

   Copy steps
   1. Disable indent-guides, linters and LSP in the buffer to test
   2. Use C-g to interrupt a hung command
   Did this fix it? Yes No

4. 4. Use a viewer for huge logs

   1. Try the vlf package (View Large Files) from MELPA
   Did this fix it? Yes No

Symptoms

Emacs freezes when opening a big log, JSON or minified file; scrolling lags; typing is delayed in large source files.

Why it happens

• Syntax highlighting and indentation on very long lines
• Extra minor modes such as indent guides, LSP or linters running on large buffers
• Emacs reading the whole file into memory

This guide also covers

• emacs slow large files
• emacs freezes opening big file
• emacs long lines slow

The same problem in other apps

All crashes, freezes & blank screens guides →

• IntelliJ IDEA Slow or Freezing (JetBrains IntelliJ)

Other GNU Emacs errors

• Emacs Failed to Verify Signature (ELPA Package Install Error)
• Emacs Slow Startup
• Emacs Native Compilation Warnings Popping Up
• Emacs Eglot / LSP Not Working
• Emacs macOS Operation Not Permitted (Documents, Desktop, iCloud)
• Doom Emacs Errors After Update or doom sync
• Emacs package-install Fails (Package Not Found or Archive Error)