While Probot doesn't have an official extension API, there are a handful of reusable utilities that have been extracted from existing apps.


probot-commands is an extension that adds slash commands to GitHub. Slash commands are lines that start with / in comments on Issues or Pull Requests that allow users to interact directly with your app.

For example, users could add labels from comments by typing /label in-progress.

const commands = require("probot-commands");

module.exports = (app) => {
// Type `/label foo, bar` in a comment box for an Issue or Pull Request
commands(app, "label", (context, command) => {
const labels = command.arguments.split(/, */);
return context.octokit.issues.addLabels(context.issue({ labels }));


probot-metadata is an extension that stores metadata on Issues and Pull Requests.

For example, here is a contrived app that stores the number of times that comments were edited in a discussion and comments with the edit count when the issue is closed.

const metadata = require("probot-metadata");

module.exports = (app) => {
app.on(["issues.edited", "issue_comment.edited"], async (context) => {
const kv = await metadata(context);
await kv.set("edits", (await kv.get("edits")) || 1);

app.on("issues.closed", async (context) => {
const edits = await metadata(context).get("edits");
body: `There were ${edits} edits to issues in this thread.`,


probot-attachments adds message attachments to comments on GitHub. This extension should be used any time an app is appending content to user comments.

const attachments = require("probot-attachments");

module.exports = (app) => {
app.on("issue_comment.created", (context) => {
return attachments(context).add({
title: "Hello World",
title_link: "https://example.com/hello",

Check out probot/unfurl to see it in action.

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