HAR File Viewer
Upload a HAR file to analyze network requests, waterfall timing, and resource breakdown. Entirely client-side.
Drop your HAR file here
or click to browse files
How to export a HAR file:
- Open Chrome DevTools (F12) → Network tab
- Reload the page to capture all requests
- Right-click the request list → "Save all as HAR with content"
How to Read a HAR File
A HAR file logs every HTTP request your browser makes when loading a page. Each entry captures the URL, method, status code, headers, timing data, and response size. The waterfall chart visualizes the sequence and overlap of these requests.
Focus on requests with long wait times (TTFB) — these indicate slow server responses. Large receive phases point to oversized assets that need compression or optimization.
Timing Phases Explained
blocked
Time spent queued before the request could be sent
DNS Lookup
Time to resolve the domain name to an IP address
connect
Time to establish a TCP connection
SSL/TLS
Time for the TLS/SSL handshake
send
Time to send the HTTP request to the server
Waiting (TTFB)
Time waiting for the server to respond (Time to First Byte)
receive
Time to download the response body
What to Look For in HAR Files
Slow TTFB
Wait times over 200ms for the main document suggest server-side bottlenecks — slow databases, no caching, or distant servers.
Too Many Requests
Pages with 80+ requests are above median. Combine scripts, use sprites, and lazy-load below-fold assets.
Missing Compression
If transfer size equals uncompressed size for text files, Brotli or Gzip compression isn't enabled on your server.
HTTP/1.1 Bottlenecks
Staircase waterfall patterns indicate HTTP/1.1 connection limits. Upgrade to HTTP/2 or HTTP/3 for multiplexing.
Third-Party Bloat
Check the domain breakdown — third-party scripts (analytics, ads) often account for 30-50% of total page weight.
Low Cache Hit Rate
A rate below 30% means most assets aren't cached. Set proper Cache-Control headers for static resources.
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Frequently Asked Questions
01What is a HAR file?
A HAR (HTTP Archive) file is a JSON-formatted log of all HTTP transactions between a browser and a website. It records every request and response, including URLs, headers, timing data, status codes, and response sizes. HAR files are used to diagnose network performance issues, debug API calls, and analyze page load behavior.
02How do I export a HAR file from Chrome?
Open Chrome DevTools (F12), go to the Network tab, load your page, then right-click the request list and select "Save all as HAR with content." Alternatively, click the download arrow icon in the Network toolbar. Make sure to check "Preserve log" if you need to capture redirects.
03How do I export a HAR file from Firefox?
Open Firefox DevTools (F12), go to the Network tab, load your page, then click the gear icon and select "Save All As HAR." Firefox HAR exports include the same timing and header data as Chrome exports.
04Is my data safe when using this HAR viewer?
Yes. This viewer runs entirely in your browser — your HAR file is never uploaded to any server. However, OWASP warns that HAR files pose a major security risk as they capture full request payloads, including plaintext passwords in postData and active Cookie session tokens. Never share raw HAR files publicly without first sanitizing sensitive headers.
05How do I read a waterfall chart?
Each horizontal bar represents one HTTP request. The bar is divided into colored phases. A "Staircase" pattern indicates sequential loading, while a "Wall" pattern suggests HTTP/2 or HTTP/3 (QUIC) multiplexing. Long "waiting" (TTFB) bars point to backend bottlenecks, and long "receiving" bars indicate large unoptimized assets. Note that with HTTP/3, connect and SSL phases often collapse into a single 1-RTT event.
06Why is my HAR file so large?
HAR files include full response bodies by default, with binary content (images, fonts) base64-encoded. A typical page load can produce a 5-50MB HAR file. To reduce size, some tools offer options to export without response bodies.
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