Parity & conformance evidence

Conformance

PDF/UA-1 and PDF/A, per document

Validated with veraPDF 1.30.2. The corpus is 5 shipped templates (invoice, receipt, report, shipping-label, letter) and 4 HTML fixtures (letterhead, dashed-borders, statement, zebra-invoice). Each PDF/A column is the archival-and-accessible render — the same file validated against the PDF/A profile and PDF/UA-1.

Document	PDF/UA-1	PDF/A-2b + UA-1	PDF/A-2a + UA-1
template/invoice	✓	✓	✓
template/receipt	✓	✓	✓
template/report	✓	✓	✓
template/shipping-label	✓	✓	✓
template/letter	✓	✓	✓
html/letterhead	✓	✓	✓
html/dashed-borders	✓	✓	✓
html/statement	✓	✓	✓
html/zebra-invoice	✓	✓	✓

Any failed profile shows its veraPDF clause list here; there are currently none. PDF/A-2u is supported and reachable but not gated separately (2a is the strictest of the three).

Determinism

Byte-for-byte, across build targets

The same document renders to byte-identical PDFs across the native binary and the WASM targets, over the four HTML fixtures. These are distinct strengths of evidence and shown as such: native, node, and web are compared byte-for-byte; the bundler target embeds a hash-identical WASM module (so it computes identically by construction) and is exercised by functional browser and workerd renders — it is not itself byte-diffed here.

Comparison	Fixture	Bytes	Identical
node↔web	letterhead	3,843	✓
native↔node	letterhead	3,843	✓
node↔web	report	5,541	✓
native↔node	report	5,541	✓
node↔web	zebra-invoice	3,603	✓
native↔node	zebra-invoice	3,603	✓
node↔web	dashed-borders	1,906	✓
native↔node	dashed-borders	1,906	✓

WASM hash-identity (bundler / web / node)

✓ identical module

sha256 445395e8dedf32aa419f8ea00289e10a…

Regression evidence

Structural assertions from Chrome reference & third-party corpus

Boolean structural assertions (page count, break positions, table structure, valign) read from Chrome's rendering of these fixtures and asserted exactly. NOT a general browser-parity claim or a measured diff.

✓ br_produces_a_multi_line_address_block✓ fixture_renders_to_a_single_page_pdf✓ heading_list_and_image_map_to_engine_node_types✓ margin_collapse_h1_to_p_gap_is_max_not_sum✓ margin_collapse_p_to_p_gap✓ stylesheet_block_is_ignored_not_rendered✓ table_maps_with_header_and_all_rows✓ unknown_css_lands_in_warnings_not_errors✓ whitespace_collapses_through_the_whole_pipeline

Hand-reduced repros distilled from the ironpress parity corpus (third-party test material, MIT). Not upstream copies.

Source: gastongouron/ironpress (MIT).

✓ break_before_page_after_content_still_breaks✓ break_before_page_on_first_block_is_suppressed✓ empty_styled_paragraph_renders_its_box✓ table_cell_vertical_align_positions_markers

Test coverage

Suite counts

Passing tests per suite, parsed from an actual run. Stated as a fact, not a percentage.

engine (lib + integration)	535 passed	✓
html crate	114 passed	✓
@formepdf/core	76 passed	✓
@formepdf/react	215 passed	✓
@formepdf/preact	4 passed	✓
@formepdf/svelte	74 passed	✓
@formepdf/vue	1 passed	✓
@formepdf/renderer	26 passed	✓
@formepdf/mcp	78 passed	✓
@formepdf/resend	5 passed	✓
@formepdf/tailwind	65 passed	✓
@formepdf/vscode	11 passed	✓
total	1,204 passed	✓

Known gaps & deliberate divergences

What isn't claimed

Not a general browser-parity claim. The Chrome-reference checks above are specific structural properties (page count, break positions, table structure, valign) read once from Chrome and asserted exactly — they do not claim pixel or layout parity with any browser.
position: absolute resolves against the nearest positioned ancestor (matching browsers), which changed in 0.15.0 — an intentional divergence from the earlier direct-parent behavior.
Collapsed table borders use a widest-wins approximation, and vertical-align: baseline maps to top in table cells where a true baseline isn't resolved — both documented, deliberate scope debts.
The supported HTML/CSS subset is explicit; anything outside it is reported as a named warning at render time, never silently dropped. See the HTML subset documentation.