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+--- Thread: How to properly send a curl post request with JSON data? or Why is my curl post request returning a 4 (/thread-how-to-properly-send-a-curl-post-request-with-json-data-or-why-is-my-curl-post-request-returning-a-4)
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How to properly send a curl post request with JSON data? or Why is my curl post request returning a 4 - DarkTrekX - 07-02-2025
"Why is my curl post request returning a 400 error?"
Hey guys,
I’m trying to send a curl post request with some JSON data, but keep getting a 400 Bad Request error.
Here’s what I’m running:
```bash
curl -X POST https://api.example.com/data -d '{"key": "value"}'
```
I’ve double-checked the JSON, and it *seems* valid. Am I missing headers? Or maybe the endpoint expects something else?
Also, is there a way to see more details about why it’s failing? Like, can I dump the full response or something?
Thanks in advance!
---
*(or alternatively...)*
"What’s the correct syntax for a curl post request with headers?"
Yo,
Need some help with a curl post request. I’m sending JSON data, but the server keeps ignoring it unless I add headers.
I’ve tried:
```bash
curl -X POST -H "Content-Type: application/json" -d '{"name": "test"}' https://api.example.com
```
But is this the right way? Do I need other headers like `Accept` or `Authorization`?
Also, does the order of flags (`-H`, `-d`, etc.) matter?
Thx!
“” - SecureLegendX - 10-03-2025
Hey! A 400 error usually means the server didn’t like your request. For a curl post request, you *definitely* need the `Content-Type: application/json` header. Try this:
```bash
curl -X POST -H "Content-Type: application/json" -d '{"key": "value"}' https://api.example.com/data
```
Also, use `-v` to see verbose output—it’ll show you the full request/response. If it’s still failing, maybe the endpoint requires auth? Check the API docs!
“” - CyberNomad99 - 13-03-2025
400 errors suck. Your JSON might be valid, but the server could be picky. Try minifying it (no extra spaces) or using `@filename.json` instead of inline JSON.
For debugging, use `-i` to include headers in the response. Or try Postman to test the API separately—way easier than fiddling with curl post requests sometimes.
“” - webPioneer77 - 15-03-2025
Yo, headers are *key* here. Your curl post request might need more than just `Content-Type`. Some APIs want `Accept: application/json` or an `Authorization` header.
Also, the order of flags doesn’t matter, but missing/extra quotes in JSON will break it. Try `jq .` to validate your JSON before sending.
“” - InvisibleOrbit99 - 27-03-2025
400 usually means malformed request. For curl post requests, double-check:
- JSON is *exactly* right (no trailing commas, quotes match).
- URL is correct (no typos).
- Headers are included (`Content-Type` is a must).
Use `curl -v` to see what’s actually being sent. If it’s still unclear, paste the verbose output here—we’ll help!
“” - cloakLeapX - 29-03-2025
Pro tip: Some APIs reject curl post requests if the `-d` data isn’t formatted *just* right. Try wrapping your JSON in single quotes and escaping double quotes inside:
```bash
curl -X POST -H "Content-Type: application/json" -d '{\"key\": \"value\"}' https://api.example.com/data
```
Or use `--data-binary` instead of `-d` to preserve formatting. Also, check if the API expects URL-encoded data instead of raw JSON.
“” - DarkTrekX - 01-04-2025
Thanks everyone! Adding `-H "Content-Type: application/json"` fixed it—turns out the server was super strict about headers.
I also tried `-v` and saw the server was expecting `Accept: application/json` too. Weird, but it works now.
Quick follow-up: How do I handle auth headers? Like, if I need to add a token, do I just slap on `-H "Authorization: Bearer token"`? Or is there a cleaner way?
“” - ProxyWarrior - 02-04-2025
If you’re stuck, try httpbin.org to test your curl post request. It echoes back your request details, so you can see what’s going wrong.
Example:
```bash
curl -X POST -H "Content-Type: application/json" -d '{"test": "data"}' https://httpbin.org/post
```
If that works, your API might have stricter rules. Also, `-v` is your best friend for debugging.