HAR File Collection

A Checklist for Court-Admissible Network Evidence

The server layer tells the truth that screenshots cannot.

Prepare a clean collection environment — fresh profile, no extensions
Configure the network tab correctly — Preserve Log, Disable Cache
Export and immediately hash the HAR file — SHA-256 before any other step
Apply a qualified timestamp — RFC 3161 eIDAS QTS at collection
Review for privilege and sensitive data — tokens, cookies, credentials
Document the collection in a witness statement — PD 57AC format for UK

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SHA-256

Hash immediately on export

The SHA-256 hash must be calculated immediately after the HAR file is exported — before any other action. Any subsequent modification breaks the hash and destroys evidential integrity.

F12

Developer tools required

HAR capture requires browser developer tools configured with Preserve Log and Disable Cache enabled before navigation begins — not after the page has loaded.

⚠️

Review before production

HAR files from authenticated sessions contain session tokens, auth cookies, and passwords in plaintext. Every HAR file must be reviewed for privilege before production.

Key Principle

A screenshot captures the browser's rendering. A HAR file captures what the server actually sent — including Date headers, CDN routing data, and response bodies that cannot be locally fabricated without detection in timing data.

What's Inside

8 steps for court-admissible HAR evidence.

I Prepare a Clean Collection Environment — fresh profile, no extensions

II Configure the Network Tab Correctly — Preserve Log, Disable Cache

III Navigate and Interact with the Target Page — capture dynamic content

IV Export and Immediately Hash the HAR File — SHA-256 before any other step

V Apply a Qualified Timestamp — RFC 3161 eIDAS QTS at collection

VI Review for Privilege and Sensitive Data — tokens, cookies, credentials

VII Document the Collection in a Witness Statement — PD 57AC format for UK

VIII Understand HAR Limitations — WebSockets, HTTPS decryption, extensions