How to Trace Redirects with cURL and Command Line

cURL is the single best tool for tracing redirects. It shows you exactly what happens at the HTTP level — no browser cache, no cookies, no JavaScript interference. Just raw requests and responses.

Here is every cURL command you need for redirect debugging, from simple one-liners to scripted bulk checks.

The Essential Command

curl -sIL "https://example.com/old-page"

This follows the entire redirect chain and prints every response header. The flags:

• -s — silent mode, suppresses the progress bar
• -I — HEAD request, fetches headers only (no body)
• -L — follow Location headers (follow redirects)

The output shows each hop:

HTTP/2 301
location: https://www.example.com/old-page

HTTP/2 301
location: https://www.example.com/new-page

HTTP/2 200
content-type: text/html

Two redirects, then a 200. That is a redirect chain — and it should probably be flattened to one hop.

Extract Just the Status Codes and Locations

Full headers are noisy. Filter to only the status lines and Location headers:

curl -sIL "https://example.com/old-page" 2>&1 | grep -iE "^(HTTP/|location:)"

Output:

HTTP/2 301
location: https://www.example.com/new-page
HTTP/2 200

Clean, scannable, and easy to pipe into other tools.

Measure Redirect Timing

Every redirect hop costs time. Measure it:

curl -sIL -o /dev/null -w "redirects: %{num_redirects}\ntotal_time: %{time_total}s\nfinal_url: %{url_effective}\nfinal_code: %{http_code}\n" "https://example.com/old-page"

Output:

redirects: 2
total_time: 0.847s
final_url: https://www.example.com/new-page
final_code: 200

Follow Redirects with a GET Request

Some servers behave differently for HEAD (-I) vs GET requests. If you suspect this, use GET but discard the body:

curl -sL -o /dev/null -D - "https://example.com/old-page"

• -D - dumps headers to stdout
• -o /dev/null discards the response body

This sends a full GET request at each hop but still shows you all headers.

Limit the Number of Redirects

Prevent infinite loops from hanging your terminal:

curl -sIL --max-redirs 10 "https://example.com/old-page"

The default is 50 redirects. For debugging, 10 is more than enough — if a chain exceeds 10 hops, something is very wrong.

Verbose Mode for Full Debugging

When you need everything — request headers, response headers, TLS handshake details:

curl -vL "https://example.com/old-page" 2>&1 | grep -E "^[<>*]"

Lines starting with > are sent by cURL (request). Lines starting with < are received from the server (response). Lines starting with * are connection info.

Send Custom Headers

Test how redirects behave with specific user agents or cookies:

# Test as Googlebot
curl -sIL -A "Googlebot/2.1" "https://example.com/old-page"

# Test with a specific cookie
curl -sIL -b "session=abc123" "https://example.com/old-page"

# Test with a custom header
curl -sIL -H "X-Forwarded-Proto: https" "https://example.com/old-page"

Bulk Redirect Checking with cURL

Check a list of URLs from a file:

while IFS= read -r url; do
  result=$(curl -sIL -o /dev/null -w "%{http_code} %{num_redirects} %{url_effective}" "$url")
  echo "$url -> $result"
done < urls.txt

For a TSV-formatted report:

echo -e "original_url\tfinal_code\tredirects\tfinal_url"
while IFS= read -r url; do
  curl -sIL -o /dev/null \
    -w "$url\t%{http_code}\t%{num_redirects}\t%{url_effective}\n" \
    "$url"
done < urls.txt

Speed Up Bulk Checks with xargs

Process multiple URLs in parallel:

cat urls.txt | xargs -P 10 -I {} curl -sIL -o /dev/null \
  -w "{} -> %{http_code} (%{num_redirects} redirects) -> %{url_effective}\n" "{}"

-P 10 runs 10 requests concurrently. Adjust based on your connection and the target server's tolerance.

Compare Expected vs Actual Redirects

Create a CSV of expected redirects and validate them:

# expected.csv format: source_url,expected_destination
while IFS=, read -r source expected; do
  actual=$(curl -sIL -o /dev/null -w "%{url_effective}" "$source")
  if [ "$actual" = "$expected" ]; then
    echo "PASS: $source -> $actual"
  else
    echo "FAIL: $source -> $actual (expected: $expected)"
  fi
done < expected.csv

This is invaluable after site migrations. Export your redirect map, run this script, and catch every broken redirect before your users do.

cURL Flags Quick Reference

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cURL does not lie. It shows you exactly what the server sends, with no browser magic in between.