cURL is one of the HTTP related tools on the command line. It serves quite well for quick checks, for automation and it can be used as a library as well.
The following example commands are useful to quickly dump the headers of an HTTP response on the command line:
curl -s -D - -o /dev/null https://www.johbo.com/
This should show output like the following:
HTTP/1.1 200 OK Content-Type: text/html Content-Length: 20857 Connection: keep-alive Date: Wed, 09 Nov 2016 13:08:24 GMT x-amz-meta-s3cmd-attrs: uid:501/gname:staff/uname:johannes/gid:20/mode:33188/mtime:1478692988/atime:1478692988/md5:2e65ca3825b7a8f1a84e6dde88af8045/ctime:1478692988 Last-Modified: Wed, 09 Nov 2016 12:03:13 GMT ETag: "2e65ca3825b7a8f1a84e6dde88af8045" Server: AmazonS3 Age: 37 X-Cache: Hit from cloudfront Via: 1.1 f989b812753677758cd8909391e239ac.cloudfront.net (CloudFront) X-Amz-Cf-Id: 0hWe7fidk775BGN7Wu84Q3Mu6W3u3x-fQBHz6xMgO25OrU6_8cEITw==