RelationCanvas is a free online tool for anyone who has to keep track of a large cast of characters. Novelists use it while plotting a series, screenwriters use it to check who shares scenes with whom, and tabletop game masters use it to remember which faction owes a favor to which NPC. You place characters on an open canvas, draw lines between them, and write a label on each end of a line. That two-sided labeling matters because relationships in fiction are rarely symmetrical: a mentor may see a student as a successor while the student quietly sees a rival. When the map is ready, export it as a PNG or SVG image for a story bible, a pitch document or a campaign wiki. The tool runs entirely in the browser, needs no account, and costs nothing.