diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 6f6eafe2..5f2dcae7 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -16,6 +16,7 @@ repos:
           - id: check-json
             exclude: tsconfig\.json
           - id: check-toml
+            exclude: bad\.toml
           - id: check-xml
           - id: check-yaml
           - id: detect-private-key
diff --git a/pyscript.core/package-lock.json b/pyscript.core/package-lock.json
index fe2777b1..74698014 100644
--- a/pyscript.core/package-lock.json
+++ b/pyscript.core/package-lock.json
@@ -1,12 +1,12 @@
 {
     "name": "@pyscript/core",
-    "version": "0.1.18",
+    "version": "0.1.19",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "@pyscript/core",
-            "version": "0.1.18",
+            "version": "0.1.19",
             "license": "APACHE-2.0",
             "dependencies": {
                 "@ungap/with-resolvers": "^0.1.0",
@@ -597,9 +597,9 @@
             }
         },
         "node_modules/electron-to-chromium": {
-            "version": "1.4.519",
-            "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.4.519.tgz",
-            "integrity": "sha512-kqs9oGYL4UFVkLKhqCTgBCYZv+wZ374yABDMqlDda9HvlkQxvSr7kgf4hfWVjMieDbX+1MwPHFBsOGCMIBaFKg==",
+            "version": "1.4.520",
+            "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.4.520.tgz",
+            "integrity": "sha512-Frfus2VpYADsrh1lB3v/ft/WVFlVzOIm+Q0p7U7VqHI6qr7NWHYKe+Wif3W50n7JAFoBsWVsoU0+qDks6WQ60g==",
             "dev": true
         },
         "node_modules/entities": {
diff --git a/pyscript.core/package.json b/pyscript.core/package.json
index 91a378aa..14d68636 100644
--- a/pyscript.core/package.json
+++ b/pyscript.core/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@pyscript/core",
-    "version": "0.1.18",
+    "version": "0.1.19",
     "type": "module",
     "description": "PyScript",
     "module": "./index.js",
@@ -21,6 +21,7 @@
     "scripts": {
         "server": "npx static-handler --cors --coep --coop --corp .",
         "build": "node rollup/stdlib.cjs && node rollup/plugins.cjs && rm -rf dist && rollup --config rollup/core.config.js && npm run ts",
+        "size": "echo -e \"\\033[1mdist/*.js file size\\033[0m\"; for js in $(ls dist/*.js); do echo -e \"\\033[2m$js:\\033[0m $(cat $js | brotli | wc -c) bytes\"; done",
         "ts": "tsc -p ."
     },
     "keywords": [
diff --git a/pyscript.core/src/config.js b/pyscript.core/src/config.js
index 23a52c63..79625ee9 100644
--- a/pyscript.core/src/config.js
+++ b/pyscript.core/src/config.js
@@ -7,38 +7,96 @@ import { $ } from "basic-devtools";
 
 import allPlugins from "./plugins.js";
 import { robustFetch as fetch, getText } from "./fetch.js";
+import { ErrorCode } from "./exceptions.js";
 
-// TODO: this is not strictly polyscript related but handy ... not sure
-//       we should factor this utility out a part but this works anyway.
-import { parse } from "../node_modules/polyscript/esm/toml.js";
+const badURL = (url, expected = "") => {
+    let message = `(${ErrorCode.BAD_CONFIG}): Invalid URL: ${url}`;
+    if (expected) message += `\nexpected ${expected} content`;
+    throw new Error(message);
+};
+
+/**
+ * Given a string, returns its trimmed content as text,
+ * fetching it from a file if the content is a URL.
+ * @param {string} config either JSON, TOML, or a file to fetch
+ * @returns {{json: boolean, toml: boolean, text: string}}
+ */
+const configDetails = async (config) => {
+    let text = config?.trim();
+    // we only support an object as root config
+    let url = "",
+        toml = false,
+        json = /^{/.test(text) && /}$/.test(text);
+    // handle files by extension (relaxing urls parts after)
+    if (!json && /\.(\w+)(?:\?\S*)?$/.test(text)) {
+        const ext = RegExp.$1;
+        if (ext === "json" && type !== "toml") json = true;
+        else if (ext === "toml" && type !== "json") toml = true;
+        else badURL(text, type);
+        url = text;
+        text = (await fetch(url).then(getText)).trim();
+    }
+    return { json, toml: toml || (!json && !!text), text, url };
+};
+
+const syntaxError = (type, url, { message }) => {
+    let str = `(${ErrorCode.BAD_CONFIG}): Invalid ${type}`;
+    if (url) str += ` @ ${url}`;
+    return new SyntaxError(`${str}\n${message}`);
+};
 
 // find the shared config for all py-script elements
-let config, plugins, parsed;
+let config, plugins, parsed, error, type;
 let pyConfig = $("py-config");
 if (pyConfig) config = pyConfig.getAttribute("src") || pyConfig.textContent;
 else {
     pyConfig = $('script[type="py"][config]');
     if (pyConfig) config = pyConfig.getAttribute("config");
 }
+if (pyConfig) type = pyConfig.getAttribute("type");
 
-// load its content if remote
-if (/^https?:\/\//.test(config)) config = await fetch(config).then(getText);
-
-// parse config only if not empty
-if (config?.trim()) {
-    try {
-        parsed = JSON.parse(config);
-    } catch (_) {
-        parsed = await parse(config);
+// catch possible fetch errors
+try {
+    const { json, toml, text, url } = await configDetails(config);
+    config = text;
+    if (json || type === "json") {
+        try {
+            parsed = JSON.parse(text);
+        } catch (e) {
+            error = syntaxError("JSON", url, e);
+        }
+    } else if (toml || type === "toml") {
+        try {
+            const { parse } = await import(
+                /* webpackIgnore: true */
+                "https://cdn.jsdelivr.net/npm/@webreflection/toml-j0.4/toml.js"
+            );
+            parsed = parse(text);
+        } catch (e) {
+            error = syntaxError("TOML", url, e);
+        }
     }
+} catch (e) {
+    error = e;
 }
 
 // parse all plugins and optionally ignore only
 // those flagged as "undesired" via `!` prefix
 const toBeAwaited = [];
 for (const [key, value] of Object.entries(allPlugins)) {
-    if (!parsed?.plugins?.includes(`!${key}`)) toBeAwaited.push(value());
+    if (error) {
+        if (key === "error") {
+            // show on page the config is broken, meaning that
+            // it was not possible to disable error plugin neither
+            // as that part wasn't correctly parsed anyway
+            value().then(({ notify }) => notify(error.message));
+        }
+    } else if (!parsed?.plugins?.includes(`!${key}`)) {
+        toBeAwaited.push(value());
+    }
 }
+
+// assign plugins as Promise.all only if needed
 if (toBeAwaited.length) plugins = Promise.all(toBeAwaited);
 
-export { config, plugins };
+export { config, plugins, error };
diff --git a/pyscript.core/src/core.js b/pyscript.core/src/core.js
index 56c81c14..d1403394 100644
--- a/pyscript.core/src/core.js
+++ b/pyscript.core/src/core.js
@@ -11,7 +11,7 @@ import { Hook } from "../node_modules/polyscript/esm/worker/hooks.js";
 
 import sync from "./sync.js";
 import stdlib from "./stdlib.js";
-import { config, plugins } from "./config.js";
+import { config, plugins, error } from "./config.js";
 import { robustFetch as fetch, getText } from "./fetch.js";
 
 const { assign, defineProperty, entries } = Object;
@@ -128,74 +128,81 @@ const workerHooks = {
 };
 
 // define the module as both `<script type="py">` and `<py-script>`
-define(TYPE, {
-    config,
-    env: `${TYPE}-script`,
-    interpreter: "pyodide",
-    ...workerHooks,
-    onWorkerReady(_, xworker) {
-        assign(xworker.sync, sync);
-    },
-    onBeforeRun(pyodide, element) {
-        currentElement = element;
-        bootstrapNodeAndPlugins(pyodide, element, before, "onBeforeRun");
-    },
-    onBeforeRunAsync(pyodide, element) {
-        currentElement = element;
-        bootstrapNodeAndPlugins(pyodide, element, before, "onBeforeRunAsync");
-    },
-    onAfterRun(pyodide, element) {
-        bootstrapNodeAndPlugins(pyodide, element, after, "onAfterRun");
-    },
-    onAfterRunAsync(pyodide, element) {
-        bootstrapNodeAndPlugins(pyodide, element, after, "onAfterRunAsync");
-    },
-    async onInterpreterReady(pyodide, element) {
-        if (shouldRegister) {
-            shouldRegister = false;
-            registerModule(pyodide);
-        }
-
-        // ensure plugins are bootstrapped already
-        if (plugins) await plugins;
-
-        // allows plugins to do whatever they want with the element
-        // before regular stuff happens in here
-        for (const callback of hooks.onInterpreterReady)
-            callback(pyodide, element);
-
-        if (isScript(element)) {
-            const {
-                attributes: { async: isAsync, target },
-            } = element;
-            const hasTarget = !!target?.value;
-            const show = hasTarget
-                ? queryTarget(target.value)
-                : document.createElement("script-py");
-
-            if (!hasTarget) {
-                const { head, body } = document;
-                if (head.contains(element)) body.append(show);
-                else element.after(show);
-            }
-            if (!show.id) show.id = getID();
-
-            // allows the code to retrieve the target element via
-            // document.currentScript.target if needed
-            defineProperty(element, "target", { value: show });
-
-            // notify before the code runs
-            dispatch(element, TYPE);
-            pyodide[`run${isAsync ? "Async" : ""}`](
-                await fetchSource(element, pyodide.io, true),
+// but only if the config didn't throw an error
+error ||
+    define(TYPE, {
+        config,
+        env: `${TYPE}-script`,
+        interpreter: "pyodide",
+        ...workerHooks,
+        onWorkerReady(_, xworker) {
+            assign(xworker.sync, sync);
+        },
+        onBeforeRun(pyodide, element) {
+            currentElement = element;
+            bootstrapNodeAndPlugins(pyodide, element, before, "onBeforeRun");
+        },
+        onBeforeRunAsync(pyodide, element) {
+            currentElement = element;
+            bootstrapNodeAndPlugins(
+                pyodide,
+                element,
+                before,
+                "onBeforeRunAsync",
             );
-        } else {
-            // resolve PyScriptElement to allow connectedCallback
-            element._pyodide.resolve(pyodide);
-        }
-        console.debug("[pyscript/main] PyScript Ready");
-    },
-});
+        },
+        onAfterRun(pyodide, element) {
+            bootstrapNodeAndPlugins(pyodide, element, after, "onAfterRun");
+        },
+        onAfterRunAsync(pyodide, element) {
+            bootstrapNodeAndPlugins(pyodide, element, after, "onAfterRunAsync");
+        },
+        async onInterpreterReady(pyodide, element) {
+            if (shouldRegister) {
+                shouldRegister = false;
+                registerModule(pyodide);
+            }
+
+            // ensure plugins are bootstrapped already
+            if (plugins) await plugins;
+
+            // allows plugins to do whatever they want with the element
+            // before regular stuff happens in here
+            for (const callback of hooks.onInterpreterReady)
+                callback(pyodide, element);
+
+            if (isScript(element)) {
+                const {
+                    attributes: { async: isAsync, target },
+                } = element;
+                const hasTarget = !!target?.value;
+                const show = hasTarget
+                    ? queryTarget(target.value)
+                    : document.createElement("script-py");
+
+                if (!hasTarget) {
+                    const { head, body } = document;
+                    if (head.contains(element)) body.append(show);
+                    else element.after(show);
+                }
+                if (!show.id) show.id = getID();
+
+                // allows the code to retrieve the target element via
+                // document.currentScript.target if needed
+                defineProperty(element, "target", { value: show });
+
+                // notify before the code runs
+                dispatch(element, TYPE);
+                pyodide[`run${isAsync ? "Async" : ""}`](
+                    await fetchSource(element, pyodide.io, true),
+                );
+            } else {
+                // resolve PyScriptElement to allow connectedCallback
+                element._pyodide.resolve(pyodide);
+            }
+            console.debug("[pyscript/main] PyScript Ready");
+        },
+    });
 
 class PyScriptElement extends HTMLElement {
     constructor() {
@@ -226,7 +233,8 @@ class PyScriptElement extends HTMLElement {
     }
 }
 
-customElements.define("py-script", PyScriptElement);
+// define py-script only if the config didn't throw an error
+error || customElements.define("py-script", PyScriptElement);
 
 /**
  * A `Worker` facade able to bootstrap on the worker thread only a PyScript module.
diff --git a/pyscript.core/src/plugins/error.js b/pyscript.core/src/plugins/error.js
index 58484df5..68abe3f4 100644
--- a/pyscript.core/src/plugins/error.js
+++ b/pyscript.core/src/plugins/error.js
@@ -24,7 +24,7 @@ hooks.onBeforeRun.add(function override(pyScript) {
 // Error hook utilities
 
 // Custom function to show notifications
-function notify(message) {
+export function notify(message) {
     const div = document.createElement("div");
     div.className = "py-error";
     div.textContent = message;
diff --git a/pyscript.core/test/bad.toml b/pyscript.core/test/bad.toml
new file mode 100644
index 00000000..b79b726d
--- /dev/null
+++ b/pyscript.core/test/bad.toml
@@ -0,0 +1 @@
+files = [
diff --git a/pyscript.core/test/config-url.html b/pyscript.core/test/config-url.html
new file mode 100644
index 00000000..8d4c7251
--- /dev/null
+++ b/pyscript.core/test/config-url.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>PyScript Next Plugin</title>
+  <link rel="stylesheet" href="../dist/core.css">
+  <script type="module" src="../dist/core.js"></script>
+  <py-config src="bad.toml" type="toml"></py-config>
+</head>
+</html>
diff --git a/pyscript.core/test/config.html b/pyscript.core/test/config.html
new file mode 100644
index 00000000..e9f0af02
--- /dev/null
+++ b/pyscript.core/test/config.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>PyScript Next Plugin</title>
+  <link rel="stylesheet" href="../dist/core.css">
+  <script type="module" src="../dist/core.js"></script>
+  <py-config>
+    files = [
+  </py-config>
+</head>
+</html>
diff --git a/pyscript.core/types/config.d.ts b/pyscript.core/types/config.d.ts
index 6507150f..2d5eceee 100644
--- a/pyscript.core/types/config.d.ts
+++ b/pyscript.core/types/config.d.ts
@@ -1,2 +1,3 @@
 export let config: any;
 export let plugins: any;
+export let error: any;
diff --git a/pyscript.core/types/plugins/error.d.ts b/pyscript.core/types/plugins/error.d.ts
index cb0ff5c3..5c76300b 100644
--- a/pyscript.core/types/plugins/error.d.ts
+++ b/pyscript.core/types/plugins/error.d.ts
@@ -1 +1 @@
-export {};
+export function notify(message: any): void;