MD ReaderWhat are the .md files Claude Code and Codex create?
If you give work to an AI coding agent like Claude Code or Codex, files ending in .md start appearing in your project. They look messy in Notepad, full of # and **. Nothing is broken: they're markdown documents, the same format AI assistants use for their answers. Agents use it because it's plain text that both people and AI can read.
The files you're likely to see
| File | What it is |
|---|---|
README.md |
Explains what the project is and how to run it |
CLAUDE.md |
Standing instructions that Claude Code reads for the project |
AGENTS.md |
Standing instructions for agents, used by Codex and others |
PLAN.md, TODO.md, NOTES.md |
Plans, task lists and notes, when you or the agent choose to keep them |
CHANGELOG.md |
A record of what changed in each version |
Names other than the first three vary from project to project, so read one if you're not sure what it's for.
Be careful with CLAUDE.md and AGENTS.md. Changing them changes how the agent behaves in that project. Reading them is always safe.
Why you'd want to read them
These files are where the agent explains itself: what it planned, what it did, what's left. If you skip them, you end up trusting a summary in the chat. They're also long, and easier to read away from your desk than in a terminal.
Reading them on your phone
These tools usually run on a computer, so the file has to reach your phone first:
- Send the file to yourself. Google Drive, an email attachment and a USB cable all work.
- On your phone, open it with MD Reader: tap the file and choose MD Reader, or use Open file in the app.
Headings, tables, code blocks with syntax highlighting, math and Mermaid diagrams are shown formatted. Front matter appears as a card, and tags like <example>, which are common in instruction files, are shown as written instead of disappearing.
MD Reader doesn't sync with your computer and doesn't connect to Claude Code or Codex. What you open is the copy you sent over. Send it again when the agent updates it. Step-by-step instructions are in how to open .md files from Google Drive.
Going through a whole folder
Agents rarely stop at one file. With the folder workspace (coming soon in Pro), you'll be able to copy a folder to your phone, open it, search all its documents and follow links between them.
Changing a plan from your phone
Tick a checkbox in a task list while reading and it's saved to the file right away. To change wording, tap Edit and type on the formatted page, with no symbols to remember (more on editing). If the file came from an app that only allows reading, MD Reader asks you to save a copy. To use your changes in the project, send the file back to your computer.