What this changes
Local preview feels fast, but it creates a trust problem: if the page refreshes before every edit is committed, uncommitted work can disappear or be drawn twice after save.
ArchitectureBrowser-native document runtime architectureA public architecture view of Browser Core: browser-side preview, PDFium-backed rendering, deterministic operations and backend-authoritative export.RuntimeA browser-side runtime for safe realtime document interactionHow Browser Core coordinates browser-local preview, runtime readiness, replayable operations, safe compositing and backend-authoritative export.Render graphRender graph planning for safe browser PDF previewHow Browser Core turns local document edits into structured visual responsibilities, command buffers, tile resolution and safe final preview output.PDFium WASMPDFium WASM for accurate browser-side PDF previewHow Browser Core uses PDFium WebAssembly for local page rastering, text awareness, textless tiles and safer live PDF previews.Textless tilesTextless tiles for cleaner PDF text editing previewsHow Browser Core removes old PDF text from live preview with small PDF-aware clean tiles instead of fake white overlay masks.Local-firstLocal-first PDF preview with backend authorityHow Browser Core gives PDF editing immediate browser-side preview while keeping save, export and persisted document state backend-authoritative.Operation replayOperation replay for refresh-safe document previewsHow Browser Core keeps local edits visible across refreshes while preserving backend-authoritative save and export.Dirty renderingDirty rendering for focused, safe PDF preview updatesHow Browser Core tracks what changed in the live preview using dirty nodes, dirty regions, command buffers and safe final compositing.Debug visibilityDebug visibility for browser-side PDF runtimesHow Browser Core makes local PDF preview behavior observable across operations, render graph state, dirty rendering, tiles, interaction and performance.Technology previewTechnology preview status for Browser CoreCurrent Browser Core technology preview status: browser runtime active, PDFium-backed preview path, backend-authoritative export and roadmap limits.RoadmapBrowser Core engineering roadmapThe Browser Core roadmap for stable local PDF editing, safer visual cleanup, broader document coverage and production-grade save/export workflows.SDK directionFuture SDK direction for embedded document runtimesFuture SDK direction for embedding Browser Core style document runtime capabilities into document products.ArticleWhy PDF editors feel slowBackend render loops make every edit wait for network and regeneration. A browser runtime can make preview feel immediate.ArticlePDFium WASM browser renderingWhere PDFium WebAssembly fits in a browser-side preview path for page raster work, text readiness and clean composition.ArticleTextless tile renderingWhy source-suppressed tiles are cleaner than white overlay masks for PDF text replacement previews.ArticleLocal-first document runtimeHow browser-owned preview sessions and backend-authoritative export can work together without pretending the browser is the final source of truth.ArticleRender graph document editingA public render graph story for document preview, affected regions and predictable compositing.ArticleDirty region rendering in the browserWhy affected-region rendering matters when small edits should not redraw the entire document preview.ArticleOperation replay for document editingRecovering local preview state with deterministic operations while clearing committed work after backend save.ArticleBrowser runtime vs backend render loopA practical comparison of local interactive preview and backend-authoritative PDF save/export.ArticleDebug visibility for document enginesWhy document runtimes need visible health, replay status, provider state and frame timing without exposing private internals.ArticleGPU document rendering roadmapHow GPU compositing can evolve browser-native document runtimes after the safe Canvas/PDFium-backed path is established.
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Operation replay for refresh-safe document previews
Operation Replay keeps local edits visible and deterministic across refreshes, reloads and browser-side runtime restarts without making the browser the final PDF authority.
Technology previewPDFium WASM activeReplay enabled
Runtime pipeline
From PDF bytes to final composite, all inside the browser preview path.
01Backend preview
02Operation log
03Replay
04Render graph
05Safe composite
06Commit cleanup
Local-firstDeterministicReal-time previewBackend-authoritative export
Browser Core approach
Runtime-first preview
Browser Core stores meaningful local edits as deterministic operations. After refresh, it loads the backend preview, restores the local operation log, rebuilds the render graph and draws the same safe composite. After backend save, committed operations are removed from replay so edits are not duplicated.
What this solves
Restores uncommitted local edits after refresh
Keeps preview behavior consistent by replaying through the render graph instead of pixel patches
Prevents saved edits from appearing twice after backend preview refresh
Supports local-first interaction while keeping backend persistence authoritative
Current status
Refresh-safe local preview
Deterministic operation order
Commit cleanup after save
Replay diagnostics surfaced
Backend remains source of truth
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Technology preview