Resume a download with Range

# resume a partially downloaded file automatically:
curl -C - -O https://example.com/big.iso

# or request an explicit byte range:
curl -r 1048576- -o part.bin https://example.com/big.iso
#   -> 206 Partial Content

// fetch bytes starting at an offset (e.g. after 1 MiB already saved)
const res = await fetch('https://example.com/big.iso', {
  headers: { Range: 'bytes=1048576-' }
});
console.log(res.status); // 206 Partial Content
console.log(res.headers.get('Content-Range')); // bytes 1048576-.../<total>

import os, requests

path, url = 'big.iso', 'https://example.com/big.iso'
have = os.path.getsize(path) if os.path.exists(path) else 0
headers = {'Range': f'bytes={have}-'}

with requests.get(url, headers=headers, stream=True) as r:
    r.raise_for_status()  # 206 if resumed, 200 if server ignores Range
    with open(path, 'ab') as f:  # append mode
        for chunk in r.iter_content(8192):
            f.write(chunk)