Paste CSV with your x-axis labels in the first column and one column per line series. Choose a line style, colour theme and whether to show point markers and value labels, then export SVG or PNG.
The tool computes a 'nice' scale rather than using your raw minimum and maximum. It rounds the interval to a friendly 1, 2, 2.5, 5 or 10 times a power of ten so the gridlines land on readable round numbers, and it always includes zero when your data crosses it.
Straight joins the points with direct segments, which is the most honest option for measured data. Smooth fits a Catmull-Rom curve for a softer look, and stepped holds each value until the next reading, which suits things like price changes or stock levels.
Blank or non-numeric cells are treated as gaps rather than zeros, so the line breaks and resumes instead of falsely dropping to the baseline. This keeps charts of partially collected data truthful.