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HAR File Viewer

Load and analyze HTTP Archive (.har) files locally to debug API requests, headers, and performance timelines.

Drag & Drop .har file here

or click to browse your local device

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Analyzing Network Traffic with HTTP Archives (HAR)

Debugging complex web applications often requires deep visibility into the network layer. Whether you are troubleshooting API latency, inspecting Cross-Origin Resource Sharing (CORS) errors, or verifying authentication payloads, the HTTP Archive (HAR) format provides a comprehensive blueprint of a user's session[cite: 4]. The RapidCalc HAR Viewer allows developers to upload these archives and reconstruct the exact sequence of HTTP transactions without transmitting the potentially sensitive log data to an external server.

Navigating the HAR Viewer Interface

When you load a HAR file into the viewer, the raw JSON object is parsed and organized into a master-detail interface similar to the network tab found in Chrome or Firefox DevTools. This allows you to audit the lifecycle of a web page systematically:

  • Request List (Master Pane): Displays a chronological sequence of all network entries recorded during the session. Each entry is tagged with its HTTP Method (GET, POST, PUT), the endpoint URL, and the server's HTTP Status Code (e.g., 200 OK, 404 Not Found, 500 Internal Error).
  • Headers Tab: Exposes both the Request Headers sent by the client and the Response Headers returned by the server. This is critical for debugging Content-Type mismatches, caching directives (like ETag or Cache-Control), and authorization tokens.
  • Payload Tab: If the request utilized a POST or PUT method, this tab decodes the postData object. It reveals the exact JSON body, URL-encoded form data, or GraphQL query submitted to the backend API.
  • Response Tab: Displays the raw textual body returned by the server. If the server returned an API error payload or validation exception, it will be visible here.
  • Timing Tab: Breaks down the granular milliseconds spent during DNS resolution, TLS handshakes, Time to First Byte (TTFB), and content download phases.

HAR Viewer vs. HAR Sanitizer

While both tools handle HTTP Archives, their purposes differ significantly. The HAR Viewer is a diagnostic tool used to *read* and analyze the contents of the file visually. Conversely, the HAR Sanitizer is a security tool used to modify the file. If you record a network session and need to share that file with a third-party support team, you should always run it through a sanitizer first to redact sensitive cookies and passwords, and then use a viewer to verify the redaction was successful.

Security and Zero-Server Processing

Network logs inherently capture sensitive state data, including active session cookies and Bearer tokens. Uploading a HAR file to a remote cloud viewer exposes your application's current authentication state to potential interception. The RapidCalc HAR Viewer mitigates this risk through a strict client-side architecture. Using JavaScript's native File API, the tool parses the JSON string entirely within your browser's local sandbox memory[cite: 4]. When you close the tab, the data is instantly purged, ensuring absolute compliance with enterprise security and privacy protocols.