DiffLines

DiffLines is a tiny and portable application that gives you the possibility to compare the content of very large text files by placing them side by side, highlighting the differences. It offers support for files with up to 4GB in size.

Portable tool with a simple GUI

There is no setup pack involved. Instead, you can copy the downloaded files to a preferred directory on the disk or to a removable storage unit, in order to seamlessly launch DiffLines on any PC with little effort. It doesn't need DLLs or other components to work properly, nor does it add new entries to the system registry.
When it comes to the interface, the utility opts for a standard window with a neatly structured layout, where you can select two files to compare by resorting to the built-in file browser. Unfortunately, it's not explicit concerning the supported file types. We've noticed that it works with .txt and .rtf format.

Compare text between two documents

With the click of a button, the text is compared and displayed in the main window, highlighting the different lines of text to help you spot them easier. Moreover, you can take into account or ignore case sensitive mode, together with spaces and tabs.
The display font and colors can be customized when it comes to equal, different and blank lines, as well as reverted to default. In addition, you can synchronize the text between the two documents, skip to the next or previous difference using hotkeys, resort to a simple search tool, as well as view the start or end of the selection.

Evaluation and conclusion

It worked smoothly in our testing, without causing the operating system to hang, crash or indicate errors. System resources consumption was minimal, since it required a low amount of CPU and RAM to work properly.
To sum it up, DiffLines may not come packed with a particularly rich set of options and customization preferences, but it offers a simple solution for comparing text between two documents to identify the same and different lines.