CEFRLex's EFLLex is very useful for sorting into CEFR levels.

I can use this data for making Quizlet lists, homework tasks, or for reference when creating materials or for student reference in productive language tasks.

It's also useful for quickly finding WHERE in your text a phrase is, or for deciding whether you should teach a word this week or next week (it might appear frequently in this week's material, and only once in next week's).

Any text editor will do this job. I have used Notepad++ for many years (still free!).

Its visual interface is easy for students to understand. They can look at sample essays, and then upload their own essays and see what coherence looks like.

It is especially good at showing whole-document features.

Once you have analyzed a text, you can SAVE THE URL and give it to your students for an overview of reading or listening.

There are several tools you can use.

I think this kind of analysis helps students notice their own progress, and also encourages them to use those "swamp" words that fall between rock-solid high-frequency vocabulary and more recently-acquired intermediate vocabulary.