Stop Paying for Slack Alerts: Send Sentry Errors to Slack for Free

Source: Dev.to

Tired of paying for Sentry’s Slack integration? Good news: you don’t have to.
With a simple setup using Sentry webhooks, Vercel Edge Functions, and Slack’s free chat.postMessage API, you can receive real‑time error notifications in Slack—without a premium plan.

Why Pay for What You Can Build?

Sentry’s built‑in Slack integration is behind a paywall. For indie developers and small projects, that cost often isn’t justified.

Instead, you can:

• Use Sentry’s webhook integration
• Catch events with a Vercel Edge Function
• Send formatted messages using Slack’s free API

Same result. Zero extra cost.

Step 1: Set Up the Sentry Webhook

1. Open your Sentry project settings.
2. Go to Legacy Integrations → Webhooks.
3. Add a new webhook (you’ll paste your Vercel function URL here after deployment).

Sentry will now send error events to your custom endpoint.

Step 2: Create the Vercel Edge Function

If you’re new to Vercel, it’s a serverless platform that runs code at the edge with a generous free tier.

We’ll create an Edge Function that:

• Receives Sentry events
• Formats them using Slack Block Kit
• Sends them to Slack via the API

export const config = {
  runtime: 'edge',
};

const sendMessage = async (
  channel,
  { level, formatted, environment, email, title, culprit, project }
) => {
  const isError = level === "error";

  const blocks = [
    {
      type: "section",
      text: {
        type: "mrkdwn",
        text: `${isError ? ":red_circle:" : ""} *${title}*`,
      },
    },
    {
      type: "section",
      fields: [
        { type: "mrkdwn", text: `*Environment:*\n${environment}` },
        { type: "mrkdwn", text: `*Level:*\n${level}` },
        { type: "mrkdwn", text: `*Project:*\n${project}` },
      ],
    },
    {
      type: "section",
      fields: [{ type: "mrkdwn", text: `*User:*\n${email}` }],
    },
    { type: "divider" },
    {
      type: "section",
      text: { type: "mrkdwn", text: `*Message:*\n${formatted}` },
    },
    {
      type: "section",
      text: { type: "mrkdwn", text: `*Culprit:*\n${culprit}` },
    },
    { type: "divider" },
  ];

  await fetch("https://slack.com/api/chat.postMessage", {
    method: "POST",
    headers: {
      "Content-Type": "application/json; charset=utf-8",
      Authorization: `Bearer ${process.env.SLACK_ACCESS_TOKEN}`,
    },
    body: JSON.stringify({ channel, blocks }),
  });
};

export default async (req) => {
  const body = await req.json();

  const {
    project,
    culprit,
    event: {
      level,
      logentry: { formatted },
      user: { email },
      environment,
      metadata: { title },
    },
  } = body;

  await sendMessage(process.env.CHANNEL_ID, {
    level,
    formatted,
    environment,
    email,
    title,
    culprit,
    project,
  });

  return new Response("Event received");
};

What This Does

• Receives error events from Sentry.
• Formats a structured Slack message using Block Kit.
• Posts directly to Slack with an OAuth token.

Step 3: Create and Configure Your Slack App

1. Go to .
2. Create a new app in your workspace.
3. Under OAuth & Permissions, add the scope chat:write.
4. Install the app to your workspace and copy the OAuth Bot Token.

Add the following environment variables in Vercel:

• SLACK_ACCESS_TOKEN – the bot token you just copied.
• CHANNEL_ID – the ID of the Slack channel that should receive alerts.

Step 4: Deploy to Vercel

1. Push the code to GitHub.
2. Import the repository into Vercel.
3. Add the environment variables (SLACK_ACCESS_TOKEN, CHANNEL_ID).
4. Deploy.

After deployment, copy the Edge Function URL and paste it into your Sentry webhook settings.

Step 5: Test It

Trigger a test error in Sentry. If everything is configured correctly, a clean, structured error notification will appear in Slack within seconds.

Why This Setup Wins

• Completely free.
• Real‑time notifications.
• Fully customizable Slack formatting.
• Serverless and low‑maintenance.
• Works on Sentry’s free plan.

Grab the Code & Customize It

Feel free to adapt this setup for your own workflow:

• Add severity filtering.
• Route different projects to different channels.
• Change formatting for staging vs. production.

If this helped you save money or improve your monitoring, consider starring the repository and sharing it with other developers.

GitHub Repository

Happy building 🚀