Open huge files instantly — every time.

Open any gigantic log or text file and read, scroll and search from the very first moment — even at 51 GB / 890M lines.

Buy UwView Pro (one-time or monthly)　｜　Download the free version

▶ A 1-minute walkthrough (instant open, search, color highlight, block save)

Unlike other viewers, viewing is instant on the first open and every open after. UwView lets you view and search the whole file the moment it opens (other viewers show only the head until indexing finishes). Indexing runs in the background and line numbers appear once it finishes. Because UwView Pro saves the index and compression, the 2nd open onward is instant, with line numbers.

Take the “waiting” out of huge files

Server logs, security logs, OSM data, AI corpora — tens of GB and hundreds of millions of lines take minutes just to open, and minutes again to search. That wait piles up many times a day. With UwView Pro you can browse the entire file the moment it opens — indexing and the compressed cache are built in the background, so you can scroll and search from start to end without waiting for them to finish (viewers that block on indexing keep the middle and end of the file out of reach until it’s done). And because UwView Pro saves the index and compression, the 2nd open onward is instant, with line numbers.

Three benefits (all measured)

1. Instant to open and use, every time — read, scroll and search any huge file from the moment it opens (indexing runs in the background; line numbers appear once it finishes). UwView Pro saves the index and compression to a .uwvz sidecar, so the 2nd open onward is instant, with line numbers (re-open in about 0.02–0.07 s; klogg re-indexes every time (~110 s) and shows only the top until indexing is done).

2. Faster search — through the compressed cache, about 9× for literal / case-insensitive (14 s vs 120–135 s) and about 4.4× for regex.

3. Store at 1/9 — archive a log at about 1/9 of its size (48 GB → 5.3 GB, checksum-protected) and open it directly, without extracting.

Measurement conditions: 47.73 GB / 892,239,125-line OSM japan-latest.osm / external USB SSD 0.41 GB/s / 32 GB RAM / compared with klogg 24.11.0. Hit counts matched exactly between the two. Numbers are not rounded.

Note on file size: “48 GB” is 47.73 GiB (bytes / 1024^3), rounded. macOS reports it as 51.25 GB (SI, / 1000^3). It is the same file (51,254,526,392 bytes).

The numbers, at a glance (klogg vs UVP, 3 sizes × 3 storage tiers)

Fig 1: total time to open the same file twice — lower is better. “Open” = index-build time for UVP vs time-until-viewable for klogg (measuring UVP by time-to-view would be near-instant, so we deliberately use its index-build time).

Fig 2: full-text search time (log scale, avg of 10 words, cold read) — lower is better. Hit counts verified identical to klogg.

A full feature comparison of klogg, free UwView and UwView Pro is here: the complete comparison — klogg’s advantages are listed honestly too.

Main features

• Instant open — browse the whole file the moment you open it, without waiting for indexing.
• Color highlighter — colorize multiple keywords at once; bundled presets, save and export sets.
• Right-click to colorize — select a word, right-click, pick a color; every occurrence lights up at once.
• Fast search with history and saved filters — result list, context view, save frequent searches.
• Block (rectangular) selection and copy — pull just the vertical columns out of fixed-width logs (Pro only).
• Session restore, recent files and favorites — pick up right where you left off.
• .uwvz archive — store at 1/9 and open directly, checksum-protected.
• Japanese encoding auto-detect (Shift-JIS / EUC-JP), append-follow (Tail), and an English / Japanese UI.

Pricing

Buy now (choose one-time or monthly)

• Payment is handled by a Merchant of Record (Polar); prices are in US dollars.
• After purchase, a license key starting with UVP-… and a download arrive from Polar. Paste the key into the app under Settings → License to activate the Pro features (see Help).

Requirements

Available for Windows, macOS and Linux.

• macOS 11 or later (Apple Silicon / Intel). Developer ID signed and Apple-notarized, so it launches without warnings.
• Windows 10 / 11 (x64 / ARM64). Unzip and run. (Currently unsigned, so Windows SmartScreen may warn on first launch — choose “More info → Run anyway”. SHA256 provided.)
• Linux (x86_64 / ARM64). Extract the tar.gz and run (SHA256 provided).

The free version (UwView) already lets you experience instant open of huge files and Japanese auto-detection → Download

Verify your download (SHA256)

After purchase, verify the downloaded file (macOS / Linux: shasum -a 256 <file>; Windows: certutil -hashfile <file> SHA256).

6828c5883dc1e13fa6c9e8cfff809d63a789b7f0032a4edc781d998fbe68fd97  UwViewPro-1.2.1-win-x64.zip
b62da23b375c99d45c7afa70625a8fe94a806207fbb7827be6d4236eed0ef22e  UwViewPro-1.2.1-win-arm64.zip
0755f1afe8803bb89da5ec3817f6e99805ae7f3168bf9d633500b2242047dee1  UwViewPro-1.2.1-mac-arm64.dmg
149fbebd88dcacaeb3a0a7cc36649e4706c436fdc7559aea7399976db32d8236  UwViewPro-1.2.1-mac-x64.dmg
a0dc8b7eb564be6246ce4bd3df9126de6b76cb2eff0d9a83a95b3693999b43e9  UwViewPro-1.2.1-linux-x86_64.tar.gz
469100789b71c486aa537f0dde5dfd459e6d10f5ebd3f2efdb1182cad8bccd32  UwViewPro-1.2.1-linux-aarch64.tar.gz

FAQ (excerpt)

• How is it different from the free version? Both let you read and search a huge file from the moment it opens. UwView Pro saves the index and compression, so the 2nd open onward is instant with line numbers, plus much faster search and 1/9 archiving. Basic viewing, search and color-coding are in the free version too.
• Which OS? Windows 10/11, macOS 11+, and Linux (x86_64). One license covers every OS.
• One-time vs monthly? One-time owns this major version forever; monthly includes the latest updates and is good for trying it out.
• Refunds? Payment is via a Merchant of Record (Polar). See Support and the terms shown at checkout.

More: Help ｜ Support ｜ Source (GitHub)

Changelog

v1.2.1 (2026-07) — a stability update (includes everything from v1.2.0)

• Faster scrolling in the search-results list (only visible rows are drawn) — the more hits, the bigger the win.
• Fixed a blank screen when dragging the scrollbar all the way to the bottom.
• “Include line numbers” now applies to every output (rectangular selection and copy/save of selected rows). The results popup keeps its scroll position and ±N setting when reopened.
• From v1.2.0: fully icon-based toolbar, session-restore fix (resume from where you closed), and a fix to the search “Next” starting point.

Full notes (including the free edition): see the GitHub release notes.

From the developer: a list of my apps, Kindle books and open-source projects is on GitHub: amru195704.