Aug 30, 20263 min read

Only the pictures already inside your page can appear in the picture you save

Tearline is one custom element that wraps any HTML you have already written and prints it out as a thermal receipt, then saves that receipt as a picture your users can post. It is for a developer building the share image at the end of something: a listening history, an order summary, a year in review.

What you get is a tag you put around your existing headings, tables and lists, and three ways to hand a reader the file: save it, take the raw file, or take an address you can drop straight into an image. It is free. MIT licence, no dependencies, no build step, installed either as a single script tag or with npm i @compound/tearline.

Watch the Tearline, Any HTML, printed as a receipt, one custom element, zero dependencies demo

The rule of the medium

Saving a receipt works by handing the browser a drawing of the paper with every word and every style written inside it. That drawing is sealed off, and it cannot reach out over the network for anything. A photograph pulled in by address never arrives.

That rule is not Tearline's, and it is not negotiable. It applies to every share-image feature that goes through the same door.

Tearline product page: HTML-to-thermal-receipt converter with demo barcode output, The tool renders custom HTML as printed receipts, shown with working barcode example output.

The browser does not tell you

Measured on the live product on 2026-08-23, the browser does not refuse the drawing when a photograph cannot be fetched. Not for a photograph from the same site, not for one from another site, not for one served with permission to share, not even for an address that returns nothing. It finishes the drawing and paints its own small broken-image icon where the photograph should be. A receipt carrying a photograph 654 pixels tall came back with a 16 pixel icon in its place, and the whole card was 600 pixels shorter than the one on screen. No error appeared anywhere.

That is the expensive version of this. Someone looks at a receipt, saves it, posts it, and the thing they posted is not the thing they were looking at.

Tearline, screenshot of the landing page

What exports, and what is refused

What is on the paper	What the export does	Why
A photograph from the same site	Refuses, and names the address	The sealed drawing reaches nothing, not even its own site
A photograph from another site	Refuses, and names the address	Same
A photograph served with permission to share	Refuses	Permission to share does not put the file inside the drawing
An address that returns nothing	Refuses	It would paint the browser's icon instead
A picture embedded directly in the page	Exports	The picture travels inside the receipt
No picture at all	Exports	Nothing to lose
A picture tag with no address	Exports	It paints nothing on screen either, so the file still matches

Tearline, the thermal receipt the component prints from ordinary HTML, and the PNG a user exports and posts. The deliverable is the printed output, not a document.

The refusal is made before the drawing is built

Any picture inside the receipt whose address is not embedded in the page stops the export up front, carrying the same sentence a reader was always meant to get plus the address that caused it. We ran that against five pictures that have to be refused and three that must not be, and the browser's own failure handler stays behind it as a second line.

The seed does the rest: the same seed always draws the same torn edge and the same barcode, so the saved file is the receipt the reader was shown.

Play with it here: https://tearline.thecompound.tech/kd

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One shipped product, taken apart, once a month. What it does, what it cost to build, what the pipeline behind it looks like, and what the numbers did, read off the repository and the live site, not written from memory. Join the list.

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