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Log File Viewer

Open multi-gigabyte log files instantly — chunked Web Worker indexing and virtual scrolling handle 10GB+ files without freezing your tab. 100% client-side: your log data never leaves your browser.

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Instant, Any Size

A Web Worker indexes the file in 50MB chunks and builds a lightweight byte-offset table — the file itself is never loaded into memory.

Constant Memory Scrolling

Only the handful of rows on screen are ever read and decoded, on demand, straight from the file — whether it's 1MB or 100GB.

Full-File Search

Search runs asynchronously in the background and streams results as it scans, so you can start jumping to matches before it finishes.

How to Open a Large Log File

  1. Drop a log file onto the box above, or click to browse — any size, any extension.
  2. Wait for indexing. A Web Worker scans the file in 50MB chunks to build a byte-offset index — this is typically close to disk read speed.
  3. Scroll, search, and jump to matches. Only the visible rows are ever decoded, so scrolling stays smooth regardless of file size.

How It Stays Fast at 10GB+

Most browser-based file tools read the whole file into a JavaScript string — fine for kilobytes, but a multi-gigabyte log file would either crash the tab or freeze it for minutes. This tool never does that. A Web Worker reads the file in 50MB chunks and records only the byte offset of every 128th line, off the main thread. That tiny offset table is enough to know exactly where any line starts, so the viewer can jump straight to the bytes for whatever rows are currently on screen — typically fewer than 100 at a time — decode just those, and discard everything else. The file itself is never fully loaded into memory.

Supported File Types

Any plain-text file, regardless of extension — there's no allowlist. That covers:

  • .log and .txt files of any kind
  • Syslog, and Apache/Nginx access and error logs
  • Application, server, and system logs
  • JSON Lines / NDJSON (one JSON object per line)
  • CSV and other delimited text exports
  • Kubernetes, Docker, and cloud log exports (CloudWatch, Stackdriver, and similar)
  • Extensionless files, or files with unusual or custom extensions

Before indexing, the tool samples the first 64KB and shows a warning if the file looks binary (a compiled executable, image, or archive) rather than text — but it's just a warning, not a block, so you can open it anyway. Only UTF-8 (and plain ASCII, which is a subset) text is decoded correctly today; UTF-16 and other encodings aren't supported yet.

Frequently Asked Questions

Does this upload my log file anywhere?

No. The file is read directly by your browser and never leaves your device — there is no upload and no server involved. This matters especially for logs, which often contain IP addresses, API keys, session tokens, stack traces, and other sensitive data: none of it is ever transmitted, logged, or stored anywhere outside your machine.

How large a file can it actually open?

It's designed for 10GB+ files. The chunked index and virtual scrolling mean memory use stays roughly constant regardless of file size.

Why does the scrollbar feel less precise on very large files?

Once a file has hundreds of millions of lines, one pixel of scroll necessarily represents many lines — the same tradeoff tools like VS Code's large-file mode make. Use the Go to line box or jump-to-match navigation for exact positioning.

Does search find matches across the whole file, or just what's visible?

The whole file. Search runs in a background Web Worker and streams matches back as it scans, so you can start jumping to results before the full scan finishes.

What file types can I open?

Any plain-text file — there's no extension restriction. See Supported File Types above for the full list.

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