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Alex Spinov
Alex Spinov

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9 cURL Tricks Every Developer Should Know (I Use #6 Daily)

#beginners #tutorial #linux #discuss

cURL is the Swiss Army knife of the internet. But most developers only use curl URL and call it a day.

Here are 9 tricks that took my API debugging from frustrating to effortless.

1. Pretty-Print JSON Responses 

curl -s https://api.github.com/users/torvalds | python3 -m json.tool
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Or with jq:

curl -s https://api.github.com/users/torvalds | jq '.name, .public_repos'
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No more squinting at wall-of-text JSON.

2. See Full Request/Response Headers 

curl -v https://httpbin.org/get 2>&1 | head -20
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The -v flag shows DNS resolution, TLS handshake, all headers. Use -I for headers only:

curl -I https://dev.to
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3. POST JSON Data 

curl -X POST https://httpbin.org/post \
  -H "Content-Type: application/json" \
  -d '{"name": "Alex", "role": "developer"}'
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Forget Postman for quick tests.

4. Follow Redirects 

curl -L https://bit.ly/some-link
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Without -L, cURL stops at 301/302. Debug redirect chains:

curl -L -v https://short.link 2>&1 | grep "< location"
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5. Download With Progress Bar 

curl -# -O https://example.com/large-file.zip
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Resume interrupted downloads:

curl -C - -O https://example.com/large-file.zip
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6. API Timing (My Daily Driver) 

curl -o /dev/null -s -w "DNS: %{time_namelookup}s\nConnect: %{time_connect}s\nTTFB: %{time_starttransfer}s\nTotal: %{time_total}s\n" https://api.example.com/health
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I run this every morning against production APIs. If TTFB spikes above 500ms, something is wrong.

7. Custom Headers 

curl -H "Authorization: Bearer TOKEN" \
     -H "Accept: application/json" \
     https://api.example.com/data
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Stack as many -H flags as you need.

8. Upload Files 

curl -F "file=@/path/to/photo.jpg" \
     -F "description=Profile picture" \
     https://api.example.com/upload
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9. Save and Reuse Cookies 

# Save cookies
curl -c cookies.txt https://example.com/login -d "user=me&pass=secret"

# Use saved cookies
curl -b cookies.txt https://example.com/dashboard
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Perfect for testing authenticated endpoints.

Bonus: My cURL Aliases 

alias jcurl='curl -s | jq .'
alias hcurl='curl -I'
alias tcurl='curl -o /dev/null -s -w "Total: %{time_total}s\n"'
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What is your most-used cURL flag?

Drop your favorite one-liner in the comments. The weirder the better.

I write about developer tools, web scraping, and productivity. Follow for weekly tips.

More from me: 10 Dev Tools I Use Daily | 77 Scrapers on a Schedule | 150+ Free APIs

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