use-cases/codebase-onboarding.md Codex Docs, 2026-04-08 00:40 UTC → 2026-05-02 06:45 UTC

1# Understand large codebases | Codex use cases1# Understand large codebases | Codex use cases

2 2 

3Codex use cases

4 

5![](/assets/OpenAI-black-wordmark.svg)

6 

7![Codex](/assets/OAI_Codex-Lockup_Fallback_Black.svg)

8 

9Codex use case

10 

11# Understand large codebases

12 

13Trace request flows, map unfamiliar modules, and find the right files fast.

14 

15Difficulty **Easy**

16 

17Time horizon **5m**

18 

19Use Codex to map unfamiliar codebases, explain different modules and data flow, and point you to the next files worth reading before you edit.

20 

21## Best for

22 

23 - New engineers onboarding to a new repo or service

24 - Anyone trying to understand how a feature works before changing it

25 

26# Contents

27 

3[← All use cases](https://developers.openai.com/codex/use-cases)28[← All use cases](https://developers.openai.com/codex/use-cases)

4 29 

30Copy page [Export as PDF](https://developers.openai.com/codex/use-cases/codebase-onboarding/?export=pdf)

31 

5Use Codex to map unfamiliar codebases, explain different modules and data flow, and point you to the next files worth reading before you edit.32Use Codex to map unfamiliar codebases, explain different modules and data flow, and point you to the next files worth reading before you edit.

6 33 

7Easy34Easy

19 46 

20## Starter prompt47## Starter prompt

21 48 

49Explain how the request flows through <name of the system area> in the codebase.

50 Include:

51 - which modules own what

52 - where data is validated

53 - the top gotchas to watch for before making changes

54 End with the files I should read next.

55 

56[Open in the Codex app](codex://new?prompt=Explain+how+the+request+flows+through+%3Cname+of+the+system+area%3E+in+the+codebase.%0A%0AInclude%3A%0A-+which+modules+own+what%0A-+where+data+is+validated%0A-+the+top+gotchas+to+watch+for+before+making+changes%0A%0AEnd+with+the+files+I+should+read+next. "Open in the Codex app")

57 

22Explain how the request flows through <name of the system area> in the codebase.58Explain how the request flows through <name of the system area> in the codebase.

23 Include:59 Include:

24 - which modules own what60 - which modules own what

68 104 

69Use Codex to turn a game brief into first a well-defined plan, and then a real browser-based...105Use Codex to turn a game brief into first a well-defined plan, and then a real browser-based...

70 106 

71Engineering Code](https://developers.openai.com/codex/use-cases/browser-games)[![](/images/codex/codex-wallpaper-2.webp)107Engineering Code](https://developers.openai.com/codex/use-cases/browser-games)[![](/images/codex/codex-wallpaper-1.webp)

72 108 

73### Analyze datasets and ship reports109### Learn a new concept

74 110 

75Use Codex to clean data, join sources, explore hypotheses, model results, and package the...111Use Codex to study material such as research papers or courses, split the reading across...

76 112 

77Data Analysis](https://developers.openai.com/codex/use-cases/datasets-and-reports)113Knowledge Work Data](https://developers.openai.com/codex/use-cases/learn-a-new-concept)