HAR File Viewer
Load a .har file to inspect requests, timings, headers, and transfer sizes with timeline filters and a detailed waterfall, all processed client-side for privacy.
Updated
HAR file viewer
Your HAR file never leaves your browser. HAR archives can contain cookies and auth headers, so sanitize before sharing externally.
How to use HAR File Viewer
HAR File Viewer opens HTTP Archive files directly in your browser and transforms noisy network traces into a clear timeline of what happened. It validates HAR structure, extracts request and response metadata, and renders a waterfall with phase timing so you can spot slow waits, oversized payloads, and status failures quickly. Because HAR files often contain cookies, auth headers, and sensitive endpoints, the tool keeps parsing local with no uploads. Use it to debug frontend performance regressions, API latency spikes, or failed third-party calls without sharing raw archives externally.
- Load a .har or .json file, drag and drop it, or paste HAR JSON directly in the fallback textarea.
- Run parsing to validate log.entries and compute summary metrics plus waterfall positioning.
- Use search, type chips, and status-class chips to narrow the request list.
- Sort by start time, duration, or size to focus on the most important bottlenecks.
- Click any row to inspect query params, headers, MIME details, and timing breakdown values.
Your data never leaves your device — 100% private processing.
Reading waterfall timelines effectively
A HAR waterfall is most useful when each request is anchored to a common page timeline rather than viewed as isolated durations. Offset shows when a request started relative to the first request, width shows total elapsed time, and internal segments explain where time was spent: blocked, DNS, connect, TLS, send, wait, and receive. Large wait periods often indicate backend latency, while long connect or SSL phases suggest network or handshake overhead. Sorting by duration can reveal outliers, but timeline placement is what exposes dependency chains and request bursts that drive user-perceived slowness.
Security and privacy considerations for HAR debugging
HAR files routinely contain sensitive operational data: full URLs with query parameters, Authorization headers, cookies, and sometimes request bodies. That makes “open in browser only” processing critical for safe ad-hoc analysis. Even when staying local, teams should sanitize archives before sharing screenshots or logs because bearer tokens and session identifiers may remain visible in detail panels. A disciplined workflow is to inspect locally, extract only minimal findings (endpoint path, timing, status), and rotate any credentials that were captured unintentionally in exported traces from production browsers.
Worked examples
Spotting a slow API wait phase
Inputs: Filter host api.example.com and sort by duration
Result: GET /reports shows 1.8s wait with 2.1s total request time
Finding largest payload quickly
Inputs: Sort by size descending
Result: image banner.webp appears first at 1.4 MB transfer size
Reviewing failed calls only
Inputs: Enable 5xx status chip and search "checkout"
Result: Two POST /checkout retries shown with response headers and timings
Glossary
- HAR
- HTTP Archive format that records browser network activity including requests, responses, headers, and timings.
- Waterfall
- A timeline visualization showing when each request starts, how long it runs, and phase-level timing segments.
- Transfer size
- Approximate bytes transferred over the wire for a request, often using _transferSize or fallback body/header sizes.
- MIME type
- Content type metadata describing response payload format, such as JSON, CSS, image, or font.
- Status class
- HTTP response grouping by first digit: 2xx success, 3xx redirect, 4xx client error, 5xx server error.
Related reading
Frequently Asked Questions
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Why use HAR File Viewer?
- Parses HAR entries into normalized request rows with status, type, size, timing phases, and host/path details
- Computes total request count, transferred size, overall timeline duration, slowest request, and largest payload
- Provides waterfall bars on a shared page timeline to compare sequencing and concurrency at a glance
- Includes filters, sorting, and expandable request detail panels for focused debugging sessions
Common use cases
- Investigate why a page loads slowly despite good backend response times
- Find oversized API or asset responses causing bandwidth spikes in production traces
- Audit failed requests by filtering 4xx and 5xx entries from imported browser HAR logs
- Share reproducible findings internally while keeping original HAR processing private and local
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