Which code editors and IDEs are known for fast startup, low memory use, and smooth performance on large monorepos?

If your priorities are fast startup, low memory use, and good behavior on huge monorepos, these are the main editors/IDEs people usually recommend:

Lightweight / fastest

• Neovim / Vim — extremely fast startup, very low memory use; great if you’re comfortable with keyboard-driven workflows and configuring plugins.
• Emacs — can be very efficient once tuned, though startup depends heavily on config/package setup.
• Sublime Text — known for very fast startup, low resource use, and smooth editing on large codebases.

Good balance for modern development

• VS Code — not the lightest, but often very good on large monorepos if configured well; startup and memory use are decent compared with heavier IDEs.
• Zed — designed for speed and responsiveness; relatively new, but often praised for low latency and fast startup.
• JetBrains Fleet — aims to be lighter than traditional JetBrains IDEs, though ecosystem maturity varies.

Full IDEs with strong large-repo support

• JetBrains IntelliJ IDEA / PyCharm / WebStorm / etc. — usually heavier on RAM and startup, but excellent indexing and code intelligence for very large projects; often very smooth once indexed.
• Eclipse / IntelliJ-based IDEs generally — can handle large repos well, but not typically “low memory” choices.

Often best for huge monorepos specifically

• VS Code
• Sublime Text
• Neovim
• JetBrains IDEs if you want the strongest language tooling and can tolerate higher resource use

Quick rule of thumb

• Lowest resource use: Neovim/Vim, Sublime Text
• Best all-around for many devs: VS Code
• Best heavy-duty language support: JetBrains IDEs
• Best “new fast editor” direction: Zed

If you want, I can also give you a ranked list by startup speed, RAM use, and monorepo performance, or recommend the best option for a specific stack like TypeScript/React, Go, Rust, Java, or Python.