HTTP Archive (.har) Waterfall Analyzer
Inspect browser network recordings, analyze DNS, SSL, and TTFB latency bottlenecks, and visualize resource waterfall timelines directly in browser memory.
A HAR Analyzer is a web performance diagnostics utility that parses HTTP Archive (HAR) JSON log files generated by modern browser developer tools. It visualizes complete network waterfalls, dissecting individual HTTP request and response headers, SSL/TLS handshake timings, DNS lookup latencies, TCP connection overheads, content download durations, and Time To First Byte (TTFB) metrics. Frontend engineers, DevOps professionals, and web performance specialists use this tool to isolate slow API endpoints, identify render-blocking assets, analyze cache hit ratios, and troubleshoot cross-origin resource sharing (CORS) bottlenecks. Because all HAR JSON parsing, cookie inspection, and timing graph generation execute entirely client-side inside browser memory with zero external data transmissions, developers can safely analyze sensitive diagnostic traces containing authorization headers, session cookies, and private request payloads with full air-gapped confidentiality.
HTTP Archive (.har) Waterfall Analyzer
Inspect browser network recordings, analyze DNS, SSL, and TTFB latency bottlenecks, and visualize resource waterfall timelines.
Network Waterfall (4 requests)
| Status | Method | Resource Name | Size | Waterfall Timeline |
|---|---|---|---|---|
| 200 | GET | / | 12.2 KB | |
| 200 | GET | /_next/static/css/app.css | 18.0 KB | |
| 200 | GET | /_next/static/chunks/main.js | 44.1 KB | |
| 200 | GET | /api/tools | 8.2 KB |
W3C HTTP Archive (HAR 1.2) Network Timing Lifecycle
The HTTP Archive specification defines standard metrics to measure each phase of a web request. Diagnosing network latency bottlenecks requires understanding where time is spent across the connection lifecycle.
Connection & Request Phases
- Blocked / Queued: Time spent in a browser socket pool queue waiting for an available TCP connection.
- DNS Lookup: Time required to resolve the hostname to an IP address via DNS servers.
- TCP Connect & SSL Handshake: Time to establish the TCP 3-way handshake and negotiate TLS cryptographic ciphers.
- Wait (TTFB): Time spent waiting for the origin server to generate and send the first byte of response data.
- Content Download (Receive): Time required to transfer all response bytes over the network wire.
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How to Use HTTP Archive (.har) Waterfall Analyzer
Export HAR from Browser
In Chrome, Firefox, or Safari DevTools, go to the Network tab, right-click, and select "Save all as HAR with content".
Upload or Choose Preset
Click "Upload .har File" or drag and drop your .har recording, or click the Next.js SSR preset.
Analyze Waterfall Timings
Review DNS (Teal), SSL (Purple), TTFB Wait (Amber), and Content Download (Blue) timing phases for each resource.
Inspect Request Headers
Click any request row to open the side inspector drawer and examine request/response headers and query parameters.
Practical Examples & Conversions
Sample: nextjs-ssr.har (4 requests)
Waterfall timeline with TTFB wait and total transfer size
Frequently Asked Questions (PAA)
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Authoritative Standards & Citations
Calculations and algorithms on this page are implemented and verified in strict accordance with the following official technical specifications:
RFC 7519: JSON Web Token (JWT)
Standardized compact, URL-safe means of representing claims to be transferred between two parties.
Web Cryptography API Specification
Standard JavaScript API for performing basic cryptographic operations in web applications.
RFC 4122: A Universally Unique IDentifier (UUID) URN Namespace
Definition of uniform format and generation algorithms for UUIDs.