About UwView

UwView is a free text viewer for browsing gigantic text files — hundreds of millions of lines — with a small memory footprint and high speed. It is a rebuild (in Avalonia UI and .NET 10) of a large-text viewer once published on Japan’s “Vector” archive, now open-sourced on GitHub.

Ordinary editors choke around a million lines. UwView never loads the whole file into memory and draws only the lines currently on screen, so it can browse huge files in practice — RDB / XML dumps, giant logs, anything you just need to look at fast. It is a read-only viewer, not an editor.

Highlights
Requirements
Measured
An even faster edition — UwView Pro (on sale)
License
Links

Highlights

Very fast display of huge files — the file body is never resident; the index is tiny (~6 MB at 200 M lines). It shows content instantly in page mode and promotes to line mode once the index is built in the background.
Automatic encoding detection — UTF-8 / Shift-JIS / EUC-JP / UTF-16, with instant manual override (no re-indexing).
Multi-file tabs — switch files as tabs; add via drag & drop or multi-select.
Search & regular expressions — literal and regex, with match highlighting, a minimap of the hit distribution, and a popup listing only the matching lines.
Color highlighter — colorize multiple registered patterns at once, with a color-blind-friendly 32-color palette and 7 bundled presets (generic log / syslog / Web access / JSON / GNSS NMEA / GeoJSON / KML). Right-click a selected word to colorize it instantly.
Bookmarks, real-time Tail, session restore — bookmark any line, follow appended logs, and restore the previous set of files.
Identical rendering on every OS — the same look on Windows / macOS / Linux, plus a bonus browser (WASM) build.

Requirements

Desktop Windows / macOS / Linux (primary), plus a browser (WASM) build. Built on .NET 10 and Avalonia UI 12.x.

To get it and learn how to use it, see Help; to try it right away in a browser, see the WASM demo.

Measured

On an Apple Silicon Mac, a 200-million-line / 5.1 GB file builds its index in 9.7 s with a ~6 MB index. On real data — the full OpenStreetMap Japan extract as XML, ~48 GiB and 892 million lines — it holds up without breaking, and the total line count matches wc -l exactly. See the verification article on the blog.

An even faster edition — UwView Pro (on sale)

The commercial edition UwView Pro is now on sale for Windows, macOS and Linux (one license, every OS). You can read and search any huge file the moment it opens; a compressed sidecar cache then makes the second open onward instant with line numbers and speeds up full-text search, and lets you keep logs at about 1/9 the size and open them directly. $129 one-time / $9 per month. → Product page

You can view the whole file the moment you open it, even on the first open; the index is simply built on the first open, in the background (other viewers show only the head until indexing finishes). Pro is instant from the second open onward, because the index is already saved.

License

UwView (free) is provided under the PolyForm Internal Use License 1.0.0.

Free for personal use and for a company’s internal business use.
You may not redistribute it, bundle it into a product/service, resell it, or provide it to third parties. Those uses require a separate commercial (redistribution) license.
For commercial-license inquiries, use GitHub Issues.