Understand a new codebase fast

Joined a new project? This prompt turns your folder structure and main files into a guided tour: the main parts, how a request flows, where data and config live, and which ten files to read first.

text-code-codebase-onboarding-map — claude — 89 words

Act as a senior engineer giving me a tour of a codebase I just joined.

Project: [WHAT IT DOES]
Folder structure:
[PASTE THE OUTPUT OF tree OR ls -R, trimmed]
Key files:
[PASTE package.json / requirements.txt AND THE MAIN ENTRY FILE]

Explain the architecture in plain words: the main parts, how a request or action flows through them, where data is stored, and where config lives. Then give me a reading order of the ten most important files, and three small starter tasks that would teach me the codebase.

Edit in the builder Copy & open Claude ↗Copy & open ChatGPT ↗Copy & open Claude Code ↗

In Claude Code or Cursor, skip the pasting: ask it to explore the repo and write this tour for you.

Get a better result

What you will get

A plain-language tour of the architecture covering the main parts, how an action flows through them, where data and config live, a reading order of ten files and three small starter tasks.

Common mistake

The tour describes a typical app, not yours.

Fix: Paste the real folder tree and the main entry file, not just a description. Ask “only describe what appears in the files I pasted”.

Also watch for

The reading order is a list of filenames with no reason. Ask for one sentence per file saying what question it answers, and what to look for when you read it.
The starter tasks are too big. Say “each task under an hour, touching no more than two files”, such as fixing a typo in a message or adding a log line.

Try a variation: list the unknowns

Ask for “ten questions I should ask a teammate that the code cannot answer, such as why a library was chosen”. It is a good first conversation with your new team.

Still not right? Reply with this

Draw the request flow as a numbered list from the first file to the database, naming each file and function in order.