Encore Toolbar

The Encore Toolbar is a lightweight, drop-in script that adds a floating developer panel to your frontend application. It automatically intercepts all fetch() and XMLHttpRequest calls, captures trace IDs from Encore's response headers, and lets you jump directly to the corresponding trace in the Development Dashboard or Encore Cloud.

This is useful when you're building a frontend that talks to an Encore backend and want visibility into what's happening on the backend without switching to a separate tool.

Installation

Add a single <script> tag to your HTML. The toolbar will automatically initialize and begin intercepting requests.

<script src="https://encore.dev/encore-toolbar.js"></script>

The toolbar automatically detects your App ID and environment by calling the /__encore/healthz endpoint on each request's origin. If auto-detection doesn't work (for example, if have a proxy between your frontend and backend and /__encore/healthz is not exposed), you can pass them explicitly:

<script src="https://encore.dev/encore-toolbar.js?appId=my-app&envName=staging"></script>

Parameter	Description
`appId`	Your Encore app slug (the one in your `app.encore.cloud` URL).
`envName`	The environment name, e.g. `staging`, or `production`.

You can also set or change these values later in the toolbar's Settings panel.

Please note

The script patches window.fetch and XMLHttpRequest at parse time. It must be loaded before your application code and without async or defer attributes. Some HTTP libraries (like Axios) store a reference to fetch when they initialize, so if the library loads before the toolbar script, those requests won't be intercepted. Place the script tag as early as possible in your <head>.

How it works

When your frontend makes a request to an Encore backend, the backend includes an x-encore-trace-id header in the response. The toolbar reads this header and records the request along with its trace ID. Only requests that include this header appear in the toolbar.

For each captured request, the toolbar shows:

Method and URL - the HTTP method and full URL of the request.
Status code - the response status.
Request and response bodies - captured automatically.
Query parameters and cookies - parsed from the request URL and document.cookie.
Trace link - a direct link to the trace in the Development Dashboard (local) or Encore Cloud (deployed environments).
Backend logs - when running locally, the toolbar connects to the local Encore daemon and displays backend log output for the selected trace.

Troubleshooting

Requests are not being intercepted

The toolbar only captures requests that return an x-encore-trace-id response header. If your requests aren't showing up:

Verify the header is present. Open your browser's Network tab, select a request to your Encore backend, and check the response headers for x-encore-trace-id. If the header is missing, the request is not going through Encore's request handling (for example, it might be hitting a non-Encore server or a reverse proxy that strips headers).
Make sure the script loads before your app. The toolbar patches fetch and XMLHttpRequest at parse time. If your application code runs before the script is loaded, those early requests won't be captured. Move the <script> tag above your application bundle.
Check for script errors. Open the browser console and look for errors related to the toolbar script. A network failure loading the script (e.g. a Content Security Policy blocking it) will prevent it from initializing.

Trace linking is not working

If the toolbar shows "Trace link could not be created", it means the toolbar doesn't have enough information to construct a link. The toolbar needs both an App ID and an Environment name. It tries to auto-detect these from the /__encore/healthz endpoint on the request's origin.

Pass parameters explicitly. The simplest fix is to set appId and envName directly on the script tag:

<script src="https://encore.dev/encore-toolbar.js?appId=my-app&envName=staging"></script>

If you don't want to hardcode the environment name, you can add a raw endpoint that redirects to the toolbar script with the correct parameters:

package toolbar

import (
    "fmt"
    "net/http"
    "net/url"

    "encore.dev"
)

//encore:api public raw path=/encore-toolbar.js
func Toolbar(w http.ResponseWriter, req *http.Request) {
    meta := encore.Meta()
    target := fmt.Sprintf(
        "https://encore.dev/encore-toolbar.js?appId=%s&envName=%s",
        url.QueryEscape(meta.AppID),
        url.QueryEscape(meta.Environment.Name),
    )
    http.Redirect(w, req, target, http.StatusFound)
}

Then point your script tag at your own backend instead:

<script src="https://your-api.com/encore-toolbar.js"></script>

Check that healthz is reachable. The toolbar auto-detects App ID and environment by calling /__encore/healthz on the request's origin. If you have a reverse proxy or API gateway between your frontend and the Encore backend, the /__encore/healthz endpoint may not be exposed through it. In that case, either configure your proxy to forward /__encore/healthz to the backend, or pass appId and envName explicitly on the script tag.
Set values in the toolbar. Open the toolbar's Settings panel and fill in the App ID and Environment fields manually.

Backend logs are not loading

Backend log streaming only works when running locally. The toolbar connects to the local Encore daemon over WebSocket at localhost:9400 to fetch logs for a given trace.

Make sure your app is running. Backend logs require encore run to be active.
Check the environment. Log streaming is only available for the local environment. In deployed environments, use the trace link to view logs in Encore Cloud.
Verify the App ID is set. The toolbar needs a valid App ID to request logs from the daemon. If /__encore/healthz is not reachable then set the App ID via the script tag or in the toolbars Settings.