Mailward
Opens and searches Outlook PST/OST files in the browser, no Outlook install needed.
Mailward parses PST and OST archives directly in a browser Web Worker, streaming the file in 64KB pages via the File API so multi-gigabyte archives open without loading into memory and nothing is ever uploaded. It reads both PST variants (ANSI from Outlook 97-2002 and Unicode from 2003+) plus OST caches, and decodes Japanese Shift_JIS/ISO-2022-JP encodings that a common JS library can't handle. Browsing, full-text search, and single-message export are free; batch export to MBOX/EML is the paid Pro feature. The maker states plainly that a damaged PST can't be repaired here — if Windows' own scanpst can't open it, neither can Mailward.
What holds up
- +Parses the file locally in your browser — nothing is ever uploaded to a server.
- +Handles multi-gigabyte archives by streaming 64KB pages, instead of loading the whole file into memory.
- +Decodes Japanese Shift_JIS/ISO-2022-JP encodings that a common JS library can't read at all.
Mind the limits
- −Batch export to MBOX/EML is paid — free use covers only single-message export.
- −Can't repair a damaged PST file — if Windows' own scanpst tool fails on it, Mailward can't open it either.
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