Web (Kotlin/Wasm)

pdfkmp, pdfkmp-compose-resources, and pdfkmp-markdown ship a wasmJs target — PdfKmp runs in the browser. The browser exposes no PDF engine to Wasm, so the web target renders through PdfKmp's own pure-Kotlin PDF 1.7 writer (kmpwriter, common code).

Install

Add the base coordinate to your wasmJs source set (or commonMain of a multi-target project — Gradle resolves the pdfkmp-wasm-js variant automatically):

kotlin {
    sourceSets {
        commonMain.dependencies {
            implementation("io.github.conamobiledev:pdfkmp:1.2.0")
        }
    }
}

Viewer not on web

pdfkmp-viewer is not published for web — browsers ship excellent PDF viewers, so hand them the bytes instead (see below).

What works

Everything vector works exactly like the other platforms:

• Text layout (justification, wrapping, RTL alignment), tables, shapes
• Gradients, rotation / opacity, clipping
• QR codes, barcodes, charts, freeDraw
• Bookmarks / outline, named destinations (TOC), links, the info dictionary
• JPEG images and 8-bit RGB / grayscale PNG images (embedded without decoding)

The identical writer is validated on the JVM by re-parsing and rasterising its output with PDFBox, and the full common test suite also runs on actual Wasm under Node.

Fonts — embedding & coverage

The web backend embeds fonts. A PdfFont.Custom is parsed and embedded as a TrueType subset (CIDFontType2 / Identity-H with a ToUnicode CMap, so the text both renders and extracts). When a run contains code points WinAnsi can't represent and no custom font is named, the backend automatically embeds a subset of the bundled Inter instead — so Cyrillic works in the browser out of the box. Plain Latin (WinAnsi) text still uses Standard-14 Helvetica for the smallest output. All content streams are Flate-compressed by a pure-Kotlin DEFLATE implementation.

Font coverage caveats

Three honest limits remain (each warned through PdfLog):

• Only TrueType-outline TTFs embed. A CFF / OpenType-CFF (.otf) custom font can't be embedded and falls back to Helvetica.
• No synthetic bold / italic. A single-face custom font is embedded as-supplied; a bold or italic style over it reuses that one face unchanged. (The four bundled Inter faces are selected by weight / style.)
• Coverage is gated by the font's own glyphs. Inter covers Latin + Cyrillic; scripts it lacks (CJK, Arabic, …) render as missing-glyph boxes unless you supply a PdfFont.Custom with the right coverage.

Current limits

Each is warned through PdfLog and skipped:

Web backend limitations

• Palette / alpha PNGs are not supported (only 8-bit RGB / grayscale PNG + JPEG).
• Interactive form widgets, encryption, and attachments are not supported.

Viewing & saving

Viewing on the web needs no library at all:

val doc = pdf { page { text("Hello, Wasm!") } }

doc.openInNewTab()                                  // browser's own PDF viewer (Blob URL)
doc.save(StorageLocation.Downloads, "hello.pdf")    // browser download

openInNewTab() hands the bytes to the browser's own PDF viewer via a Blob URL; save(...) becomes a browser download. No embedded web viewer is planned.

Install coordinate

implementation("io.github.conamobiledev:pdfkmp:1.2.0")   // resolves pdfkmp-wasm-js for the wasmJs target

Try the sample

The repo ships a browser sample app — a button grid over the bundled Samples.* documents plus a live pdfkmp-markdown demo, every PDF generated in-browser on click:

./gradlew :sample-web:wasmJsBrowserDevelopmentRun

See also

• Platform parity — the Web column in the feature matrix.
• Fonts, i18n & RTL — the per-platform non-Latin coverage table.
• The Wasm feasibility and Streaming & memory internals notes.