Safe In-Browser Handoffs Between JSON, CSV, and Base64

Validate syntax and shape first

Pretty JSON does not prove that business rules are satisfied. Fix parse errors, then inspect required keys, types, nulls, and array structure. Decide how nested objects will be represented before moving to CSV.

Keeping records in one array makes the column set explicit. Document that numbers, booleans, and dates may become text in CSV and will not regain their original types automatically.

• Write down field types.
• Check missing and unexpected keys.
• Choose a nesting/flattening rule.

Understand the handoff lifecycle

The transfer action writes only visible output, the chosen target slug, and a timestamp to sessionStorage. The destination opens in the same tab, loads the input, and removes the record after use or twenty minutes.

Convenience does not sanitize sensitive data. Shared devices, extensions, and screenshots remain risks. Mask before conversion when needed and inspect unexpected content before running the destination tool.

Base64 is not encryption

Base64 is reversible encoding that turns bytes or Unicode into portable text. It provides no secrecy, access control, or integrity. It can help with API bodies and data URIs, but never with keeping a secret.

Check character encoding before conversion and verify the decoded value afterward. Text encoding can amplify memory use for large files, so use file-oriented workflows beyond bounded tool limits.

• Treat Base64 as public data.
• Test a Unicode round trip.
• Verify integrity separately with SHA-256 when required.