Configuration

No runtime configuration

Mail Thread Export has no options page, no settings UI, no environment variables and no stored preferences. It does not request the storage permission. Everything below is a source-level constant that takes effect after npm run build.

Render options

All of these live in src/content/exporter.js.

Value	Default	Location	Effect
Wrapper width	800px	wrapper.style.cssText	Layout width the conversation is re-flowed to before capture.
html2canvas width / windowWidth	800	generateImagePDF(), generateImage()	Must match the wrapper width, or the capture is clipped or padded.
html2canvas scale	2	generateImagePDF(), generateImage()	Device-pixel multiplier. 1 halves file size and sharpness; 3 triples memory use.
Content padding	40px	paddedContent.style.cssText	White margin around the exported content.
backgroundColor	#ffffff	both generators	Canvas background where the DOM is transparent.
useCORS	true	both generators	Attempt to load cross-origin images. Images from hosts without permissive CORS headers are dropped from the capture regardless.
foreignObjectRendering	false	both generators	Kept off — the foreignObject path is faster but renders Gmail’s DOM inconsistently.
logging	false	both generators	Set to true to get html2canvas’ own trace in the console.
Settle delay	500 ms	exportEmail()	await new Promise(r => setTimeout(r, 500)) before measuring and capturing, giving the browser time to lay out the clone and load images. Raise it for image-heavy threads.
Height measurement	paddedContent.scrollHeight + 50	exportEmail()	The + 50 is slack so the last line is never clipped.

PDF output

Value	Default	Location
Image codec embedded in the PDF	JPEG at quality 0.95	canvas.toDataURL('image/jpeg', 0.95)
Page units	px	new jsPDF({ unit: 'px' })
Page format	[canvas.width / 2, canvas.height / 2]	generateImagePDF() — the / 2 undoes scale: 2, so the page matches CSS pixels
Orientation	l if the canvas is wider than tall, otherwise p	generateImagePDF()
Filename	<subject>.pdf via pdf.save()	generateImagePDF()

Switching the codec to canvas.toDataURL('image/png') and passing 'PNG' to pdf.addImage() gives lossless output at a considerably larger file size.

Image output

Value	Default	Location
MIME type	image/png (image/jpeg when called with 'jpg')	generateImage()
Quality argument	1.0	canvas.toDataURL(mimeType, 1.0) — ignored for PNG
Download mechanism	a synthetic <a download> click	generateImage()

generateImage() already accepts 'jpg', but the injected menu only ever calls it with 'png'.

Export header

exportEmail() prepends a header block to the clone:

Value	Default	Location
Title text	filenameBase.substring(0, 100) — the conversation subject, truncated to 100 characters	h1.innerText
Title style	20px, bold	h1.style.cssText
Timestamp	new Date().toLocaleString() — the export time, not the message date, rendered in the browser locale	date.innerText
Timestamp style	11px, #5f6368	date.style.cssText
Separator	1px solid #ddd, 25px bottom margin	header.style.cssText

Font stack

forceJapaneseFont() applies one stack to the clone and to every descendant with !important:

"Hiragino Kaku Gothic Pro", "Meiryo", "Yu Gothic", "MS Gothic", "Noto Sans JP", sans-serif

This deliberately overrides whatever fonts the mail specified, to guarantee CJK glyph coverage. See the Fonts guide for how the stack resolves and how to add Noto Sans JP yourself.

Gmail selectors

cleanArtifacts() holds the list of things stripped from the clone. This is the part most likely to need maintenance, because Gmail’s obfuscated class names change without notice.

• Removed outright: the extension’s own UI, every [role="toolbar"], and elements whose data-tooltip contains Reply, Forward, Antworten or Weiterleiten.
• Hidden via display: none !important: a list of aria-label selectors (English and German), [role="alert"], roughly thirty Gmail class names (.hI, .fv, .at, .gE, .T-I, .bAo, …), and everything carrying a data-tooltip attribute.
• Heuristics: short text nodes matching known interface phrases have their nearest [role="button"] / .T-I / [data-tooltip] ancestor hidden; svg and path elements inside a button-like ancestor are hidden unless they sit inside the message body (.a3s).
• Colour normalisation: any computed background that is a light grey (channels within 10 of each other and above 200) is forced to #ffffff; the clone’s own text colour is forced to #202124.

The heuristics are aggressive

Hiding everything with a data-tooltip, and every icon inside a button-like ancestor, can also remove legitimate content from unusual messages. If part of a thread goes missing from an export, cleanArtifacts() is the first place to look.

Build configuration

webpack.config.cjs:

Setting	Value	Why
mode	production	Minified output.
entry.content	./src/content/scanner.js	The only bundled entry point.
output.path	dist/	What you load unpacked.
LimitChunkCountPlugin maxChunks	1	MV3 content scripts cannot load extra chunks at runtime, so everything must be in one file.
Font rule	asset/inline for `woff	woff2
CopyPlugin patterns	manifest.json, content/style.css, assets/, popup/, background/	Copied verbatim; the last three use noErrorOnMissing.
performance.hints	false	The bundle is legitimately large (~770 KiB) because html2canvas and jsPDF are inlined.

Manifest

src/manifest.json declares activeTab, scripting and downloads, plus the host permission https://mail.google.com/* and a <all_urls> web_accessible_resources entry for assets/*. Only the host permission is actually needed by the working code path — see Privacy & Permissions.