Visit https://jlfwong.github.io/speedscope/, then drop a profile onto the page.
Currently accepts the same folded stack format as the original FlameGraph scripts do: https://github.com/brendangregg/FlameGraph#2-fold-stacks.
For example, try dropping this file onto the browser window: https://raw.githubusercontent.com/jlfwong/speedscope/master/sample/perf-vertx-stacks-01-collapsed-all.txt