Keep lines containing a word or phrase that you specify, or keep the lines that don’t have that word or phrase (click “Show Example”).
You can also ignore case, match only whole words, and sort results. Just paste lines into the field, select options, and press Submit. Results appear at the bottom of the page.
Starting with this list:
cat
dog
mat
a big chubby hog
If you keep lines with “at” in them, you will be left with
cat
mat
If you remove lines with “at” in them, you will be left with
dog“The LORD your God is in your midst, a mighty one who will save; he will rejoice over you with gladness; he will quiet you by his love; he will exult over you with loud singing.”
– Zephaniah 3:17