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Log File Viewer

Open and read a log file in your browser, with errors and warnings easy to spot.

  • Free
  • No signup
  • Nothing uploaded
  • No watermark

Source

0 lines
1

Entries

Paste something on the left, or press Sample to load an example.

Read in this tab. Nothing you paste or open is ever uploaded.

How to Read a Log File More Easily

Log File Viewer: before and after LOG A BEFORE LOG FILEVIEWER LOG A AFTER

When a server crashes or an app misbehaves, the answer is usually buried in a log file of thousands of similar lines. This viewer splits each line into its time, its level and its message, and gives every level its own coloured badge, so errors stand out from routine chatter.

A row of totals across the top tells you at a glance how many ERROR, WARN, INFO and DEBUG lines the file contains. Open a .log, .txt or .out file, or paste lines copied from a terminal.

No software to install Free Works on any device

Steps to Scan a Log File

  1. 1. Load the log

    Pick a .log, .txt or .out file through Open file, let it fall onto the text pane, or paste lines from your terminal or hosting dashboard.

  2. 2. Check the level counts

    The Entries pane begins with the number of lines and a badge for each level found, such as ERROR 12 or WARN 40.

  3. 3. Scan the coloured rows

    Each line becomes a row with its timestamp, a level badge in red, amber, blue or grey, and the message. Red rows are the ones to read first.

Try it now

What Is a Log File?

A log file is a running diary that software writes about itself. Each line usually starts with a date and time, then a severity level, then a message. Levels run from TRACE and DEBUG for fine detail, through INFO for normal events, to WARN, ERROR and FATAL when something goes wrong. Reading them in order is how developers work out what happened just before a failure.

Why Use an Online File Viewer?

Not every computer has the right program for a YAML, VCF, SRT or log file, and installing one just to look inside is a chore. A viewer opens the file in your browser and shows it neatly next to its source text.

“Sometimes you just need to see what is inside the file.”
  • No software to install
  • Data laid out as tables
  • Subtitles shown with timings
  • Code tried out in the page
  • Colour-coded source text
  • Contacts and calendars readable
  • Works on shared computers
  • Private files stay local

Popular Uses for Code and Data Viewers

People open these when a file arrives and nothing on the computer will show it.

  • Checking a JSON response Open a JSON or YAML file as a readable tree instead of one long line.
  • Reading contact backups See the names and numbers inside a VCF file exported from a phone.
  • Opening calendar invites Read the date, time and place in an ICS file before adding it.
  • Checking subtitles View SRT or VTT subtitles with their timings to spot a missing line.
  • Reading log files Scroll through a server or app log with the lines laid out clearly.
  • Previewing CSV and TSV Look at a data file as a table without opening a spreadsheet program.
  • Trying a code snippet Run a short Python or JavaScript example from a tutorial and see the output.
  • Viewing SVG graphics See how an SVG icon or drawing looks next to the markup behind it.

What the Log Viewer Picks Out

Nine level names

TRACE, DEBUG, INFO, NOTICE, WARN or WARNING, ERROR, FATAL, CRITICAL and SEVERE, in any capitalisation.

Timestamps

ISO dates with times, with or without time zones and fractions of a second, plus plain HH:MM:SS clock times.

Colour-coded badges

Red for errors and worse, amber for warnings, blue for information and grey for debugging detail.

Totals by level

A summary line counts each severity, sorted from most to least frequent.

Why Use ToolXkit for Log File Viewer?

Your files stay with you

Everything runs inside your browser. Nothing you open or type is uploaded to a server.

File Viewers for Different Users

Developers

Inspect config, env and data files on any machine without an editor installed.

Programming students

Try small programs in Python, JavaScript or SQL without setting anything up.

IT support staff

Open logs, HAR files and settings files that users send in.

Office workers

Read contact, calendar and CSV files that arrive as email attachments.

Video editors

Check subtitle files for timing and text before a video goes out.

Data analysts

Glance at CSV, TSV, JSONL and GeoJSON files before loading them anywhere.

Best Times to View a File Online

A browser viewer is handy when you are:

  • Using a borrowed or office computer
  • Opening an unfamiliar attachment
  • Checking a file before importing it
  • Learning to code without installing
  • Debugging a settings file
  • Proofreading subtitle timings
  • Looking inside a phone backup
  • Reviewing a server log

Tips for Log Analysis

  1. Find the first red row, not the last. Later errors are often knock-on effects of the first one.

  2. Look at the timestamps just before an error. The INFO lines leading up to it usually explain what the program was doing.

  3. Huge logs are trimmed to their opening portion when opened. Copy the time window you care about and paste just that part.

  4. Logs often contain email addresses, IP numbers or tokens. Reading them here keeps that data off third-party servers.

  5. Lines without a recognised level still appear, just without a badge, so nothing is hidden from you.

Frequently Asked Questions

Answers to common questions about this tool.

How do I open a .log file?

A .log file is plain text, so Notepad or TextEdit can open it. For easier reading, open it on this page instead: each line is split into time, level and message, with errors highlighted in red.

Can I filter the log to show only errors?

There is no filter button. The level totals and red badges make errors easy to spot while scrolling. To isolate them, paste only the lines you need, or use a text filter tool first.

Which log formats does it understand?

Any line-based log where the level appears as a word and the time, if present, comes first. That covers most application, web server and framework logs, including Java, Python, Node.js and PHP output.

Why do some lines have no time or level?

Stack traces and multi-line messages continue over lines that have no timestamp of their own. They are shown as plain rows beneath the entry they belong to.

Is it safe to open production logs here?

Yes. Parsing happens in your browser tab and the log is not transmitted. That keeps customer data and internal addresses in the logs away from outside services.

Do the online compilers run real code?

Some languages, such as Python, JavaScript, TypeScript, Lua and SQL, run inside your browser. For others, the page is mainly for reading and sharing the code, so read the note on that page to know what to expect.

Does Log File Viewer cost anything or need a login?

Neither. There is no fee, no sign-up and no cap on how many files you open. It works the same on a work laptop, a home computer or a phone.

What if my file is very large?

Large logs and data files depend on your device’s memory, because the whole file is read in the browser. If a huge file feels slow, try a computer with more memory or view a smaller part of it.

Can I open a file from my phone?

Yes. Use the file picker to choose it from your phone’s storage or a downloaded attachment, and the contents appear on the page. A larger screen is easier for long files, but everything works on mobile.

Further reading

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