diff --git a/.gitignore b/.gitignore
index 294efab..954f4e4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -32,14 +32,10 @@ node_modules
 # Unpacked build output. Regenerated by "make", never edited by hand.
 build
 
-# Intermediate packages.
-logsdu-*.zip
-
-# Packaged .xpi files are NOT ignored. They are the published artifact: the
-# signed add-on is what people download and install, so it belongs in the
-# repository (or attached to a release) rather than being rebuilt by everyone
-# who wants to install it. An unsigned local build can be removed with
-# "make clean".
+# dist/ holds the publishable packages and is NOT ignored: the signed add-on
+# is what people download and install, so it belongs in the repository (or
+# attached to a release) rather than being rebuilt by everyone who wants it.
+# Local unsigned builds land there too; "make clean" removes the directory.
 
 # Exclude sourcemaps
 *.map
diff --git a/Makefile b/Makefile
index caf1f77..4479078 100644
--- a/Makefile
+++ b/Makefile
@@ -19,33 +19,41 @@
 # *  rcb@beco.cc                                                           *
 # **************************************************************************
 
-# Makefile for logsdu - build the unpacked extension into build/.
+# Makefile for logsdu - build the extension for Firefox and Chrome.
 #
 # Usage:
-#   make            # typecheck and bundle into build/
+#   make            # typecheck and bundle for Firefox into build/
+#   make chrome     # same, but with Chrome's manifest, into build/
 #   make test       # run the unit tests
-#   make xpi        # build, then package build/ as logsdu-<version>.xpi
-#   make clean      # remove build/ and the package
+#   make smoke      # check the background bundle works as a service worker
+#   make xpi        # package the Firefox build  -> dist/logsdu-<version>.xpi
+#   make crx        # package the Chrome build   -> dist/logsdu-<version>-chrome.zip
+#   make packages   # both of the above
+#   make clean      # remove build/ and dist/
+#
+# build/ holds the unpacked extension and is regenerated from scratch; dist/
+# holds the packages meant to be published, and is kept out of build/ so that
+# packaging never tries to include its own output.
 #
 # Dependencies are installed with pnpm, never npm:
 #   corepack pnpm install
 #
-# Permanent install (Firefox ESR, Developer Edition or Nightly):
-#   set xpinstall.signatures.required=false in about:config, then
-#   about:addons -> gear -> Install Add-on From File -> pick the .xpi
+# Load the unpacked build while developing:
+#   Firefox  about:debugging -> This Firefox -> Load Temporary Add-on ->
+#            build/manifest.json          (dropped when Firefox restarts)
+#   Chrome   chrome://extensions -> Developer mode -> Load unpacked -> build/
 #
-# Release Firefox refuses unsigned add-ons whatever that pref says. There the
-# same .xpi has to go through addons.mozilla.org as an unlisted add-on first,
-# which signs it automatically without publishing or reviewing it.
-#
-# Throwaway install for development: about:debugging -> This Firefox ->
-# Load Temporary Add-on -> pick build/manifest.json (dropped on restart).
+# Publishing:
+#   Firefox  upload dist/*.xpi at addons.mozilla.org
+#   Chrome   upload dist/*-chrome.zip at chrome.google.com/webstore/devconsole
 
 EXT_ID := logsdu
 VERSION := $(shell node -p "require('./package.json').version")
-XPI := $(EXT_ID)-$(VERSION).xpi
+DIST := dist
+XPI := $(DIST)/$(EXT_ID)-$(VERSION).xpi
+CRX := $(DIST)/$(EXT_ID)-$(VERSION)-chrome.zip
 
-.PHONY: all build chrome test xpi clean check-deps
+.PHONY: all build chrome test smoke xpi crx packages clean check-deps
 
 all: build
 
@@ -55,23 +63,29 @@ all: build
 test:
 	node --test "src/**/*.test.ts"
 
+# Runs the built background bundle in a service-worker-shaped sandbox, which
+# is where a Chrome-only breakage would otherwise hide until runtime.
+smoke: build
+	node tools/sw-smoke.mjs
+
 # Call the local toolchain directly, so this works regardless of how pnpm is
 # provided (corepack vs standalone). Run "corepack pnpm install" first.
 build: check-deps
 	node_modules/.bin/tsc -noEmit -skipLibCheck
 	node esbuild.config.mjs production
 
-# The same sources with Chrome's background key. Untested against Chrome; it
-# exists so the port is a build flag rather than a fork.
+# The same sources with Chrome's manifest. Firefox and Chrome disagree on the
+# background key and on the gecko block, so the manifest is generated per
+# target rather than forked.
 chrome: check-deps
 	node_modules/.bin/tsc -noEmit -skipLibCheck
 	TARGET=chrome node esbuild.config.mjs production
-	@echo "Chrome build in build/ -- load it via chrome://extensions (Developer mode)."
+	@echo "Chrome build in build/ -- chrome://extensions -> Developer mode -> Load unpacked."
 
 # An .xpi is just a zip of the extension directory, with the manifest at the
-# top level rather than inside a wrapper folder. The same file installs
-# directly on ESR and uploads to AMO for signing.
+# top level rather than inside a wrapper folder.
 xpi: build
+	@mkdir -p $(DIST)
 	rm -f $(XPI)
 	cd build && zip -qr ../$(XPI) .
 	@echo
@@ -80,7 +94,8 @@ xpi: build
 	@echo "This file is UNSIGNED. Two ways to use it:"
 	@echo
 	@echo "  Publish -- upload it at addons.mozilla.org/developers/addon/submit/"
-	@echo "    Mozilla signs it; the signed file installs on any Firefox."
+	@echo "    Listed add-ons are signed once review approves them; unlisted"
+	@echo "    ones are signed straight away."
 	@echo
 	@echo "  Install locally -- only on ESR, Developer Edition or Nightly:"
 	@echo "    1. about:config -> xpinstall.signatures.required = false"
@@ -89,9 +104,22 @@ xpi: build
 	@echo "       $(CURDIR)/$(XPI)"
 	@echo
 
+# The Chrome Web Store takes a plain zip, and does the packing into .crx itself.
+crx: chrome
+	@mkdir -p $(DIST)
+	rm -f $(CRX)
+	cd build && zip -qr ../$(CRX) .
+	@echo
+	@echo "Built: $(CURDIR)/$(CRX)"
+	@echo "Upload it at chrome.google.com/webstore/devconsole"
+	@echo
+
+# Both packages. The Firefox build runs last so build/ is left in the state
+# the development instructions assume.
+packages: crx xpi
+
 clean:
-	rm -rf build
-	rm -f $(EXT_ID)-*.xpi $(EXT_ID)-*.zip
+	rm -rf build $(DIST)
 
 # Fail with a useful message rather than a confusing "tsc: not found".
 check-deps:
diff --git a/README.md b/README.md
index 3f8c549..15da879 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ Once it is published, from addons.mozilla.org. Until then, build it yourself:
 
 ```
 corepack pnpm install     # first time, or after a dependency change
-make xpi                  # typecheck, bundle, and package logsdu-<version>.xpi
+make xpi                  # typecheck, bundle, and package dist/logsdu-<version>.xpi
 ```
 
 `make xpi` prints the full path of the file and how to install it. The package
@@ -118,23 +118,56 @@ check.
 
 ## Chrome
 
-`make chrome` builds it. The only difference is the background key: Firefox MV3
-uses an event page, Chrome MV3 requires a service worker, so the manifest is
-generated per target rather than duplicated. Everything else -- `chrome.*`
-namespace, MV3, no Firefox-only APIs -- is already shared.
+```
+make chrome               # unpacked Chrome build in build/
+make crx                  # package it as dist/logsdu-<version>-chrome.zip
+```
 
-It has not been tested against Chrome. Do not assume it works.
+Load `build/` via `chrome://extensions` -> Developer mode -> **Load unpacked**,
+or upload the zip at
+[the Web Store dashboard](https://chrome.google.com/webstore/devconsole).
+
+One codebase, two manifests. Chrome MV3 requires a background *service worker*
+and rejects Firefox's event-page `background.scripts`; Firefox needs the gecko
+block that Chrome has no use for. `esbuild.config.mjs` writes the right manifest
+per target, so the port is a build flag rather than a fork. Everything else --
+the `chrome.*` namespace, MV3, the permission model -- is shared.
+
+Two things that differ in practice, both handled:
+
+- **Icons must be raster.** Chrome does not accept SVG in `icons`, so the PNGs
+  in `icons/` are generated from `logsdu.svg` and both browsers use those.
+- **Service workers have no `window` or `document`.** A stray reference through
+  a shared import would break Chrome only, silently, at runtime. `make smoke`
+  runs the built background bundle in a worker-shaped sandbox to catch that.
+
+What has been verified: Chrome 151 loads the build without errors, and the
+background bundle registers exactly one content script for exactly the
+configured origin. What has **not** been verified is a real login against a live
+portal in Chrome.
+
+A caveat that applies to both browsers: the page-world filler is injected as a
+`<script src>` tag, which a site's Content-Security-Policy can refuse. Portals
+that send no CSP -- the common case for this kind of form -- are unaffected. A
+portal that does would need the filler registered as a `MAIN` world content
+script instead.
 
 ## Development
 
 ```
 corepack pnpm install
 make test                 # unit tests
+make smoke                # background bundle under a service worker
 make                      # typecheck and bundle into build/
+make packages             # both publishable packages into dist/
 corepack pnpm run dev     # rebuild on change
 make clean
 ```
 
+`build/` is the unpacked extension and is regenerated from scratch every time.
+`dist/` holds the packages meant to be published, and is kept separate so that
+packaging never tries to include its own output.
+
 While iterating, load the unpacked directory rather than reinstalling an `.xpi`
 each time: `about:debugging` -> **This Firefox** -> **Load Temporary Add-on** ->
 `build/manifest.json`, then press **Reload** there after each rebuild. That copy
@@ -156,6 +189,7 @@ still needs the Reload click to pick anything up.
 | `src/config.ts` | Stored values, the rate limit and the logout cooldown |
 | `src/format.ts` | Input normalisers for the three masked fields |
 | `src/options.*`, `src/popup.*` | The two bits of UI |
+| `tools/sw-smoke.mjs` | Checks the background bundle survives a service worker |
 
 ### Why two scripts instead of one
 
diff --git a/VERSION b/VERSION
index 0ea3a94..0d91a54 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.2.0
+0.3.0
diff --git a/logsdu-0.2.0.xpi b/dist/logsdu-0.3.0-chrome.zip
similarity index 51%
rename from logsdu-0.2.0.xpi
rename to dist/logsdu-0.3.0-chrome.zip
index 27205f0..19692ba 100644
Binary files a/logsdu-0.2.0.xpi and b/dist/logsdu-0.3.0-chrome.zip differ
diff --git a/dist/logsdu-0.3.0.xpi b/dist/logsdu-0.3.0.xpi
new file mode 100644
index 0000000..3583969
Binary files /dev/null and b/dist/logsdu-0.3.0.xpi differ
diff --git a/icons/logsdu-128.png b/icons/logsdu-128.png
new file mode 100644
index 0000000..bc72839
Binary files /dev/null and b/icons/logsdu-128.png differ
diff --git a/icons/logsdu-16.png b/icons/logsdu-16.png
new file mode 100644
index 0000000..9e7eb5b
Binary files /dev/null and b/icons/logsdu-16.png differ
diff --git a/icons/logsdu-32.png b/icons/logsdu-32.png
new file mode 100644
index 0000000..4f96382
Binary files /dev/null and b/icons/logsdu-32.png differ
diff --git a/icons/logsdu-48.png b/icons/logsdu-48.png
new file mode 100644
index 0000000..1bac2c6
Binary files /dev/null and b/icons/logsdu-48.png differ
diff --git a/icons/logsdu-96.png b/icons/logsdu-96.png
new file mode 100644
index 0000000..7f3ded1
Binary files /dev/null and b/icons/logsdu-96.png differ
diff --git a/package.json b/package.json
index 2b3e7c7..5471603 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "logsdu",
-	"version": "0.2.0",
+	"version": "0.3.0",
 	"description": "Browser extension that fills and submits a three-field academic portal login.",
 	"author": "Ruben Carlo Benante <rcb@beco.cc>",
 	"type": "module",
diff --git a/src/manifest.json b/src/manifest.json
index ad2c188..0e34fa1 100644
--- a/src/manifest.json
+++ b/src/manifest.json
@@ -1,13 +1,16 @@
 {
 	"manifest_version": 3,
 	"name": "logsdu",
-	"version": "0.2.0",
+	"version": "0.3.0",
 	"description": "Saves and fills logins that password managers cannot: registration number, date of birth and document number.",
 	"author": "Ruben Carlo Benante (Dr. Beco)",
 	"homepage_url": "https://code.beco.cc/beco/logsdu",
 	"icons": {
-		"48": "icons/logsdu.svg",
-		"96": "icons/logsdu.svg"
+		"16": "icons/logsdu-16.png",
+		"32": "icons/logsdu-32.png",
+		"48": "icons/logsdu-48.png",
+		"96": "icons/logsdu-96.png",
+		"128": "icons/logsdu-128.png"
 	},
 	"browser_specific_settings": {
 		"gecko": {
@@ -36,6 +39,9 @@
 	"action": {
 		"default_popup": "popup.html",
 		"default_title": "logsdu",
-		"default_icon": "icons/logsdu.svg"
+		"default_icon": {
+			"16": "icons/logsdu-16.png",
+			"32": "icons/logsdu-32.png"
+		}
 	}
 }
diff --git a/tools/sw-smoke.mjs b/tools/sw-smoke.mjs
new file mode 100644
index 0000000..de67ed2
--- /dev/null
+++ b/tools/sw-smoke.mjs
@@ -0,0 +1,135 @@
+// *************************************************************************
+// * (C)opyright 2026         by Ruben Carlo Benante                       *
+// *                                                                       *
+// * This program is free software; you can redistribute it and/or modify  *
+// *  it under the terms of the GNU General Public License as published by *
+// *  the Free Software Foundation, either version 3 of the License, or    *
+// *  (at your option) any later version.                                  *
+// *                                                                       *
+// * This program is distributed in the hope that it will be useful,       *
+// *  but WITHOUT ANY WARRANTY; without even the implied warranty of       *
+// *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        *
+// *  GNU General Public License for more details.                         *
+// *                                                                       *
+// * You should have received a copy of the GNU General Public License     *
+// *  along with this program.  If not, see http://www.gnu.org/licenses/.  *
+// *                                                                       *
+// * Contact author at:                                                    *
+// *  Ruben Carlo Benante                                                  *
+// *  rcb@beco.cc                                                          *
+// *************************************************************************
+
+// Smoke test for the background bundle under Chrome's execution model.
+//
+// Chrome MV3 runs the background as a service worker, where there is no
+// `window` and no `document`, and the global object is `self`. Firefox runs
+// the same file as an event page, where those do exist -- so a reference that
+// creeps in through a shared import breaks Chrome only, and breaks it silently
+// at runtime rather than at build time.
+//
+// This evaluates the built bundle in a worker-shaped sandbox with a stubbed
+// extension API, and asserts that it registers exactly one content script, for
+// exactly the configured origin. Run it against build/ after a build:
+//
+//   make smoke
+
+import { readFileSync } from 'node:fs';
+import vm from 'node:vm';
+
+const BUNDLE = 'build/background.js';
+const CONFIGURED_ORIGIN = 'https://portal.example.br';
+
+const permissionChecks = [];
+const registered = [];
+const listeners = {
+	onInstalled: 0,
+	onStartup: 0,
+	onRemoved: 0,
+	onChanged: 0,
+	onMessage: 0,
+};
+
+const chrome = {
+	runtime: {
+		onInstalled: { addListener: () => listeners.onInstalled++ },
+		onStartup: { addListener: () => listeners.onStartup++ },
+		onMessage: { addListener: () => listeners.onMessage++ },
+	},
+	permissions: {
+		onRemoved: { addListener: () => listeners.onRemoved++ },
+		contains: async (p) => {
+			permissionChecks.push(p.origins);
+			return true;
+		},
+	},
+	storage: {
+		local: {
+			get: async () => ({
+				config: {
+					url: `${CONFIGURED_ORIGIN}/`,
+					ra: '2000101010',
+					dn: '01/02/1999',
+					cpf: '123.456.789-01',
+					autoSubmit: true,
+				},
+			}),
+			set: async () => {},
+		},
+		onChanged: { addListener: () => listeners.onChanged++ },
+	},
+	scripting: {
+		getRegisteredContentScripts: async () => [],
+		unregisterContentScripts: async () => {},
+		registerContentScripts: async (scripts) => registered.push(...scripts),
+	},
+};
+
+// Deliberately no window and no document: referencing either must fail here
+// exactly as it would inside a service worker.
+const sandbox = { chrome, console, setTimeout, clearTimeout, queueMicrotask, URL };
+sandbox.self = sandbox;
+vm.createContext(sandbox);
+
+const failures = [];
+
+try {
+	vm.runInContext(readFileSync(BUNDLE, 'utf8'), sandbox, { filename: BUNDLE });
+} catch (error) {
+	console.error(`FAIL: ${BUNDLE} threw on evaluation: ${error.message}`);
+	process.exit(1);
+}
+
+// Give the top-level resync() a turn of the event loop to settle.
+await new Promise((resolve) => setTimeout(resolve, 50));
+
+for (const [name, count] of Object.entries(listeners)) {
+	if (count !== 1) failures.push(`${name} registered ${count} times, expected 1`);
+}
+
+if (registered.length !== 1) {
+	failures.push(`registered ${registered.length} content scripts, expected 1`);
+} else {
+	const script = registered[0];
+	const expected = `${CONFIGURED_ORIGIN}/*`;
+	if (script.matches?.length !== 1 || script.matches[0] !== expected) {
+		failures.push(`matches ${JSON.stringify(script.matches)}, expected ["${expected}"]`);
+	}
+	if (script.js?.[0] !== 'content.js') {
+		failures.push(`js ${JSON.stringify(script.js)}, expected ["content.js"]`);
+	}
+	if (script.persistAcrossSessions !== false) {
+		failures.push('persistAcrossSessions must be false, or startup registers twice');
+	}
+}
+
+if (permissionChecks.length !== 1) {
+	failures.push(`checked permissions ${permissionChecks.length} times, expected 1`);
+}
+
+if (failures.length > 0) {
+	for (const failure of failures) console.error(`FAIL: ${failure}`);
+	process.exit(1);
+}
+
+console.log('ok - background bundle runs as a service worker');
+console.log(`ok - registers content.js for ${CONFIGURED_ORIGIN}/* and nothing else`);