Is it safe to analyze sensitive HAR files here?

Yes, 100% safe. This tool executes entirely inside your browser's local client memory using JavaScript. Your HAR files, authentication tokens, cookies, and passwords are never transmitted to any external server.

A HAR (HTTP Archive) file is a standardized JSON-formatted log that records all web browser interactions with a server, including request URLs, response headers, status codes, cookies, and detailed network timing phases.

What causes high TTFB (Time to First Byte) in a waterfall?

High TTFB indicates server-side processing delays, slow database queries, backend computation bottlenecks, or lack of caching. If TTFB is slow across static files, it often points to geographical distance or lack of a Content Delivery Network (CDN).

How can I sanitize sensitive credentials before sharing a HAR file?

Before sharing a HAR file with third-party support teams, open it in a text editor or sanitization utility and search for 'Authorization', 'Cookie', and 'Set-Cookie' fields to replace private passwords, API keys, or session cookies.

⚡ 100% Client-Side In-Browser HAR File Waterfall Inspector

HAR Analyzer: Inspect Network Waterfalls & HTTP Logs

Analyze HTTP Archive (.har) files securely in your browser. Inspect visual waterfall timing breakdowns, request & response headers, payloads, cookies, and TTFB latency with zero server uploads.

📂

Drop your .har file here or click to browse

100% Private: All processing runs locally inside your browser memory

Request Details

How to Export & Analyze a HAR File in 3 Steps

Record in Browser DevTools

Press F12 in Chrome, Edge, or Firefox to open Developer Tools. Navigate to the Network tab and reproduce your web issue.

Export the .HAR Log

Click the down-arrow icon (Export HAR) or right-click any network request and select "Save all as HAR with content" to download the archive.

Drop & Inspect Waterfalls

Drag the file into our analyzer. Click any row to inspect HTTP status codes, response headers, cookies, and identify high TTFB latency bottlenecks.

The Complete Guide to HAR Files, Waterfalls & Web Performance

HTTP Archive (HAR) is a standardized JSON format used across all modern browsers and performance tools to record and benchmark web page transactions.

Why In-Browser Client-Side Analysis is Essential for Security

HAR files capture raw HTTP traffic. When you export network logs from an authenticated web session, that file typically includes:

Session Tokens & Bearer Keys: Recorded in the Authorization header.
Session Cookies: Login cookies (such as connect.sid or AWS tokens) stored in Cookie and Set-Cookie headers.
PII & POST Payloads: Submitted passwords, usernames, payment tokens, or API secrets.

Uploading a HAR file to third-party cloud servers risks exposing sensitive credentials. HAR Analyzer 1io processes the entire JSON archive locally inside your browser's V8 runtime. Disconnecting your internet connection does not interrupt the tool, ensuring zero cloud leaks.

Deciphering the Network Waterfall Timing Phases

Every network transaction in a HAR file breaks down into distinct chronological phases:

Blocked / Stalled: Time the browser spent waiting in the socket queue because of connection limits (browsers limit HTTP/1.1 connections to 6 per domain).
DNS Lookup: Time taken to resolve the domain name to an IP address via recursive DNS resolvers.
TCP Connect: Round-trip time required to complete the initial SYN/ACK handshake with the server.
SSL / TLS Handshake: Cryptographic negotiation time for establishing HTTPS encryption.
Waiting (TTFB - Time to First Byte): Latency spent waiting for the server to process the request and send the first byte of data. High TTFB points to slow backend queries or heavy server compute.
Content Download: Time spent receiving the remaining response bytes across the network connection.

Network Latency Phases & Diagnostic Matrix

Reference guide for diagnosing web bottlenecks through HAR timing metrics:

Timing Phase	Target Healthy Duration	Probable Cause of Delay	Recommended Optimization
DNS Lookup	< 20 ms	Slow ISP DNS resolver, lack of Anycast	Switch to Cloudflare (1.1.1.1) or Google (8.8.8.8), enable DNS prefetching
Initial Connect (TCP)	< 50 ms	High physical distance to origin server	Implement a Content Delivery Network (CDN) edge cache (Cloudflare/Fastly)
SSL / TLS Handshake	< 60 ms	Old TLS 1.2 protocol, slow cipher suites	Upgrade to TLS 1.3 with 0-RTT session resumption
Waiting (TTFB)	< 200 ms	Uncached database queries, slow backend PHP/Node	Implement edge page caching, Redis/Memcached, query indexing
Content Download	Depends on asset size	Uncompressed assets, massive image payloads	Enable Brotli/Gzip compression, convert images to modern WebP/AVIF

Frequently Asked Questions

How do I open a HAR file on my computer?

Simply drag and drop your .har file into the box above. You don't need to install any heavy desktop programs or register for an account.

Can I analyze HAR files generated from Charles Proxy or Fiddler?

Yes. The HTTP Archive specification follows a universal open JSON schema (v1.2) supported by Chrome, Firefox, Safari, Edge, Fiddler, Charles Proxy, and Postman.

What is the maximum HAR file size this tool can process?

Because processing runs locally inside your browser's 64-bit JavaScript memory, our engine easily handles large HAR archives (over 100 MB containing thousands of requests) smoothly without timing out.

Why do some network requests show in red?

Requests colored in red indicate failed HTTP transactions, such as 4xx client errors (404 Not Found, 403 Forbidden, 401 Unauthorized) or 5xx server failures (500 Internal Error, 502 Bad Gateway, 504 Gateway Timeout).