docs(express.json): clarify usage and add route-specific limit example

[kushal4345]

Summary

This PR updates the express.json() documentation to:

• Clarify behavior and options in a more concise way.
• Add an example showing how to set different limit values for specific routes (e.g., /upload).

Changes

• Added a "Different limits for specific routes" section with a code example.
• Maintained existing style and formatting consistent with the Express docs.
• Verified that markdown tables and headings render correctly.

Reason

Closes #1421 requests additional clarity on using express.json() with different route limits.
This helps developers quickly understand how to override defaults for specific endpoints without affecting others.

Notes

• No changes to Express codebase, only to documentation.
• Follows current contributing and formatting guidelines.

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[github-actions]

🚦 Lighthouse Results (Mobile & Desktop)

URL	Device	Perf	A11y	Best Practices
/	mobile	🔴 60	🟢 100	🟠 79
/en/blog/posts.html	mobile	🟠 76	🟢 96	🟢 96
/en/5x/api.html	mobile	🟠 76	🟢 95	🟢 96
/	desktop	🟢 99	🟢 100	🟠 78
/en/blog/posts.html	desktop	🟢 99	🟢 96	🟢 93
/en/5x/api.html	desktop	🟢 99	🟢 95	🟢 96

[ShubhamOulkar]

I don't think changes are required. Property table explained limit option very well and clear. See our use middleware page since this example explains how to use express.json() middleware.

[kushal4345]

Thanks for the review!

I understand that the property table explains the limit option, but I think this example could still add value for developers. The table shows the option in isolation, while this example demonstrates how to apply different limits for specific routes (e.g., /upload) without affecting the global middleware.

In my experience, beginners often struggle to connect configuration options to real-world route usage, so I felt this would make the docs more practical and beginner-friendly.

Of course, I’m happy to adjust the wording or placement if you think a shorter version would fit better. Please let me know your thoughts!

[ShubhamOulkar]

@kushal4345, I think updating use middleware page would be better. This page includes a built-in middleware section at the bottom.

[kushal4345]

Thanks for the suggestion

i have Added a new section titled “Different Limits for Specific Routes” to the middleware page.
This section includes a clear code example demonstrating how to set different rate limits for individual routes.
The update aims to make the middleware page more informative and helpful for developers by providing practical usage guidance.

[kushal4345]

Hi @ShubhamOulkar, I saw you requested changes, but I couldn’t find specific comments in the Files changed tab. Could you clarify what needs to be updated? I’ll make the adjustments accordingly.

[bjohansebas]

Thanks for your contribution. I agree with @ShubhamOulkar; it makes more sense for this to be under the use middleware page, not to add it in the API files, because each API describes its functionality and shouldn’t explain how to use it under different forms of middleware.

[bjohansebas]

From what I can see, you made the change in the wrong file, judging by the commit message.

[kushal4345]

Hi I’ve updated the using-middleware.md guide to include an example of applying different JSON body size limits for specific routes.

Added a code snippet showing how to set a custom limit (5mb) for /upload.
Ensured the default express.json() still applies for other routes.
Fixed formatting to properly close the markdown code block.

[bjohansebas]

In this file neither, it’s in this one.
https://github.com/expressjs/expressjs.com/blob/gh-pages/en/guide/using-middleware.md

[kushal4345]

Thanks for the clarification I’ve added the new example for different limits inside en/guide/using-middleware.md under the Built-in middleware section as suggested. Please let me know if you’d like me to adjust the placement further.

[ShubhamOulkar]

Please remove unnecessary changes

[ShubhamOulkar]

These changes are not required. Please undo it.

[ShubhamOulkar]

🤔 Should we need separate pages for explaining how to use built in middleware options?
It feels off-topic on the page

[jonchurch]

The root issue expressjs/express#3932 that inspired the linked issue is really about understanding middleware ordering and targeting specific routes with specific middleware, not about bodyParser.limit setting really.

I don't think the proposed change focused on bodyParser.limit is necessary

[karlhorky]

@jonchurch hmm not sure what you mean.

I understood expressjs/express#3932 to be about "how can I configure the /upload route with a certain limit and non-/upload routes with a different limit?" since that is the case provided in that issue description at the top of the page.

I think my issue #1421 doesn't subvert that original wish, and that the changes in this PR are helpful for understanding how to achieve this common use case.

Do you disagree with either of those things?