Small tools. A lighter day.
GreatJIN Tools is a collection of browser utilities for small, repetitive tasks without installation or registration.
Who makes these tools
GreatJIN builds and operates this service, bringing everyday and developer conversions together with explanations of their calculation methods and limitations.
Operator: GreatJIN
Contact: greatjin@greatjin.com
LinkedIn profile
Another project by the same operator, Youtube The Words, explores public YouTube comments. The two services have different features and data practices.
What can you do here?
- Video editor · Audio editor: trim local files and join them in order, without uploading them.
- IP / CIDR calculator: calculate IPv4/IPv6 ranges, counts and IP membership without making connections.
- URL encoder / decoder: convert URL components, complete URLs or form values. Entered addresses are not visited and results are never executed.
- Unicode escape converter: convert text and emoji to and from Unicode escapes. Input is never executed, stored or uploaded.
- Base64: encode Korean text, emoji and files, then restore the original data. This is an encoding, not encryption.
- Subtitle time shift: move SRT/VTT subtitles by a fixed offset. Gradually drifting synchronization requires a separate speed adjustment.
- JSON · YAML · HTML: format code for readability. Large JSON integer literals are preserved; HTML is displayed as code rather than executed.
- Date conversion & calculation: convert KST/UTC timestamps and distinguish the 100th day including the base date from 100 days later.
- RGB palette · Image editor: compare HEX/RGB colors, or crop and resize an image. The ASCII art tab turns images into text pictures to copy or save as TXT.
- Notepad: write plain text or Markdown and export TXT, MD or HTML. Autosave works only when you enable it.
- Unit converter: convert seven categories including length, mass and temperature. US/Imperial gallons and MB/MiB are distinguished, with numeric limits explained.
- Clock: use a live clock, lap stopwatch and countdown. Alerts are not guaranteed during screen lock or device sleep.
- Currency converter: look up ECB reference rates or enter a rate manually. The rate date is shown; actual bank exchange rates may differ.
Principles you can check while using the tools
Conversion text and files are not uploaded to a server. Korean and English offer the same features, with examples, instructions and error conditions. Invalid input clears results or disables the relevant actions to avoid copying stale output.
Tool inputs are not saved, except for optional notepad autosave. Clock records also reset on reload. Keep backups and check results before using them.
Currency lookup requests send currency codes to an external provider only when you click the lookup button. Amounts are not sent, and manual rate entry works without a lookup.
Bug reports and improvements
If a calculation differs from your expectations or an explanation is unclear, share the tool URL, a sample input, and expected versus actual results. Use a small reproducible example instead of sensitive original files.
How to contact us or report a bug → · Privacy notice →
Advertising and service operation
The current site code contains no ad-serving scripts. AdSense publisher verification does not mean ads are running or approval is complete. Before introducing advertising, we will update the privacy information and necessary consent steps for the actual data practices.