Usage

Exporting a conversation

1. Open https://mail.google.com/ and open a conversation, so the subject heading is visible.

2. Click the Export button immediately to the right of the subject. It is styled to match Gmail’s own pill buttons and turns blue while its menu is open.

3. Pick an entry:

   • Export as PDF — a single-page PDF containing a JPEG render of the thread.
   • Export as Image — a 2x PNG of the same render.

4. The menu entry swaps to a spinner and Processing… while the render runs, then the browser downloads <subject>.pdf or <subject>.png and the menu closes.

Clicking anywhere outside the button or the menu closes it.

What the output contains

• A header with the conversation subject (truncated to 100 characters) and the time you ran the export, in your browser’s locale format.
• The full thread as displayed, at a fixed 800 px layout width with 40 px of white padding.
• No Gmail interface: no toolbar, no reply/forward/more buttons, no stars, no labels, no banners.
• Light grey Gmail backgrounds flattened to white.

The timestamp is the export time

The date printed in the header is new Date() at export time — not the date the message was sent. Message dates remain visible inside the captured thread itself wherever Gmail was showing them.

Practical notes

Expand what you want captured first. The extension captures the DOM as it currently stands inside div[role="main"]. Collapsed messages in a long thread, truncated quoted text behind the “…” trimmed-content button, and unexpanded image attachments are captured in their collapsed state. Expand them in Gmail before clicking Export.

Scrolling does not matter. The clone is rendered off-screen at full height, so you do not need to scroll through the thread first.

Long threads take a few seconds. Rasterising at scale: 2 is CPU-bound and runs on the page’s main thread, so Gmail may feel briefly unresponsive on very long conversations.

Very long threads can hit canvas limits. Browsers cap canvas dimensions (commonly around 32,767 px per side, with an additional total-area cap). A thread that renders taller than that will fail or come back blank. Splitting the export — for example by opening individual messages — is the workaround.

Filenames come from the subject. The subject text is used verbatim as the filename base, so the browser’s own sanitising decides what happens to characters like / or :.

When something goes wrong

Symptom	Cause	Fix
No Export button	Content script not injected, or no conversation open	Reload the Gmail tab; make sure a conversation is open, not the message list
Could not detect email content. alert	h2.hP (the subject heading) was not found	Open an actual conversation; if Gmail changed its markup, the selector in detectEmail() needs updating
Export Failed: … alert	The render threw	Open DevTools; the full error is logged to the console
Blank or truncated output	Canvas size limit, or the cleanup heuristics removed too much	See the canvas note above and cleanArtifacts() in Configuration
Missing remote images	Those hosts do not send permissive CORS headers	Not fixable from a content script
CJK text renders as boxes	No CJK font installed	See the Fonts guide
The toolbar popup says Please refresh Gmail tab	The popup is not wired to the content script	Expected — use the injected Export button instead

The toolbar popup

Clicking the extension icon in the browser toolbar opens a popup with PDF, PNG and JPG cards. It does not work. The popup sends PING and EXPORT messages with chrome.tabs.sendMessage, but the content script registers no chrome.runtime.onMessage listener, so the send always rejects and the popup settles on Reload Page / Please refresh Gmail tab.

The injected Export button is the working entry point. See Architecture for what wiring it up would involve.