OpenPresent

A PowerPoint-compatible presentation engine and editor that you can run anywhere. A deterministic Rust engine reads, models, lays out and writes .pptx, and runs natively or in the browser through WebAssembly. On top of it sits an editor built to work like PowerPoint, on the web and as a desktop app, so a PowerPoint user needs no teaching.

The engine is built first, and fidelity comes before features: a deck opened and saved by OpenPresent should keep everything PowerPoint put in it.

Website and editor: https://casualoffice.github.io/openpresent/. Open a deck in the editor, or see our renders beside LibreOffice's in the slide gallery.

Pre-alpha. It opens, edits, presents, co-edits and exports decks, each in a first, thin form. See Status for exactly what works today and what is left.

Part of CasualOffice, with OpenCalc (spreadsheets) and OpenDoc (documents), whose architecture it shares.

Why another presentation editor?

Most open editors can open a .pptx. Fewer can save one back without quietly losing what they did not understand: animations they do not model, extensions from newer Office versions, a SmartArt layout, a chart's embedded workbook. The damage shows up later, for the next person who opens the file in PowerPoint.

OpenPresent is designed around that problem:

• Nothing is lost silently. Every part of a deck is either modelled or kept byte for byte, and anything that cannot be kept is named in a compatibility report.
• Edits are surgical. Saving an edited deck rewrites only the XML nodes that changed. Every untouched part keeps its exact bytes.
• Coverage is measured, not claimed. Every element, attribute and enum value in the Office Open XML schemas, 8,739 in all, is a row in a spec checklist. A row is marked supported only when code and a test deck prove it.
• Every file is treated as hostile. Zip bombs, entity expansion, path tricks, tracking links and credential-leaking UNC paths are refused or reported. Nothing is fetched and no macro ever runs.
• The engine owns text layout. Every collaborator, every export and every browser sees the same line breaks.

Status

Docs are true as of 8011d28 (2026-11-09).

Phases 0 and 1 are closed (Phase 1 signed off by the owner on 2026-11-08): every Phase 1 tier, 1A to 1N and 1R, is closed. Of 8,739 checklist rows, 7,843 are marked y or r in model, import and export; 469 more are n/a in a column that does not apply to them; the 427 others each carry a named reason in docs/spec/open-rows.tsv or are accounted for by their members, and tools/spec-audit checks every one. 66 real PowerPoint-written decks open and save with every XML part byte-identical.

Since then the work runs as vertical slices (roadmap §After Phase 1). Slices 1 to 12 are built and merged; none is closed, because each still lacks part of its end point, most often a CI browser run. What is left is named in each slice's tracker row.

| What you can do | State | Left | | --- | --- | --- | | Open a .pptx in the browser: thumbnails, zoom, Reading View, report of what a slide leaves out (slice 1) | ✅ Built, live | CI browser run over every real deck (VS-01) | | See tables, charts, SmartArt and OLE fallbacks, shadows and glows drawn (slice 2) | 🟡 In progress | Render tiers' gates (VS-02, FH-04) | | Desktop app on Linux, macOS and Windows, double-click a .pptx (slice 3) | ✅ Built; bundles green on CI at 50ea80d | Dependency policy over its lockfile, a drawn-slide check on macOS and Windows (DESK-01, DESK-02) | | Save (byte-identical when unedited), export PDF with real text, slide as PNG (slice 4) | ✅ Done (VS-04) | The owner's sign-off | | Edit text: click, type, IME, select, Bold/Italic/Underline, fonts and sizes, colour, highlight, alignment, bullets, undo (slice 5, UX-003) | ✅ Built | CI browser run, IME check (VS-15) | | Select, move, resize, rotate, multi-select, align, delete shapes, with undo (slice 6) | ✅ Built | Drag budget, groups, CI browser run (VS-14) | | Present: slide show, Presenter View, notes, PowerPoint's keys (slice 7) | ✅ Built | Automatic advance, show settings, CI run (VS-16) | | Build slides: New Slide from a layout, duplicate, hide, reorder, delete; insert text box, picture and all 187 shapes (slice 8, SHAPE-01) | ✅ Built | Change layout, shape effects, freeform (VS-08, SHAPE-02) | | Co-edit: Share a link, see each other's edits, carets and presence (slice 9) | 🟡 Built; the two-browser run passes on CI (run 42515688718 at 7bc2092) | Resume, tokens, more edits on the wire (COL-02 to COL-08) | | Transitions and animations: six of each, played in the show, Animation Pane (slice 10) | ✅ Built | Effect options, timing, goldens (VS-10) | | Insert and edit tables and charts (column, bar, line, pie), Edit Data (slice 11) | ✅ Built | Cell typing through the text engine, merge, more chart types (VS-20) | | Themes, variants, slide size, background (slice 12) | ✅ Built | Slide Master editing (DSN-01) | | File tab: rename, Info properties, Save As .pptx, .potx, .ppsx, Print; autosave and recovery in the browser | ✅ Built | Modified date stamp, atomic save, undo kept in drafts (FILE-01, SAVE-01) | | Side panes: Comments (threaded, replies, resolve, saved as modern comments), editable speaker notes, the Selection Pane (UX-011) | 🟡 Built, seen in a browser | What its row lists (UX-011) | | Hosts: WOPI, SDK, MCP (slice 13) | ⬜ Not started | VS-13 |

Fidelity, measured. On every push to main, CI draws each gallery slide with our renderer and with LibreOffice and compares them (docs/51). At 1ba6443 (run 42511686894, LibreOffice 26.2.6.3, 111 slides): on average 5.4% of pixels differ (94.6% agree), median 4.4%, SSIM 0.869; 64 slides within 5%, 14 within 1%. This is agreement with LibreOffice, not a PowerPoint match: PowerPoint itself has not yet checked our output (PV-01), and until it has nothing here claims to match it. See the gallery.

PowerPoint parity, audited. The parity audit (docs/96 §Parity today, first at 7539ea5, re-audited and kept current since) marks 352 PowerPoint features against the live editor: 63 work (17.9%), 57 work in part, 47 are present but disabled, 185 are absent, none faked. Of the 280 we mean to build, 60 work (21.4%). The first audit found 35 (9.9%).

Try it

In the browser: open the editor, then drop a .pptx on it or start from the blank deck. The deck is read and drawn inside your browser and is never uploaded.

From source. You need Rust 1.88 or later (pinned in rust-toolchain.toml).

git clone https://github.com/CasualOffice/openpresent
cd openpresent
cargo test --workspace

# Inspect any deck: structure, conformance, and anything suspicious in it
cargo run -p casual-slide-ooxml --example inspect -- path/to/deck.pptx

# Draw every slide of a deck to PNG, or the deck to PDF
cargo run --release -p casual-slide-render --example render-deck -- path/to/deck.pptx out/
cargo run --release -p casual-slide-render --example export-pdf -- path/to/deck.pptx out.pdf

The inspector prints the deck's kind and part count, plus each finding: external content that was not fetched, unsafe links, macro projects, embedded objects, and parts nothing points to.

Build and serve the editor yourself. The editor is static files plus the engine as WebAssembly:

rustup target add wasm32-unknown-unknown
cargo install wasm-pack --version 0.14.0 --locked
wasm-pack build crates/casual-slide-wasm --release --target web --out-dir "$PWD/webapp/pkg"
python3 -m http.server -d webapp 8000     # then open http://127.0.0.1:8000/editor.html

Any static web server will do (modules and the worker do not load from file://); this is how the site is self-hosted, and pages.yml does the same for GitHub Pages (webapp/README.md).

Co-edit. The collaboration server serves the editor and relays edits; it never reads a deck:

# after building webapp/pkg as above
cd server/casual-slide-collab-server
OPENPRESENT_COLLAB_FILES=../../webapp cargo run --release
# listens on 127.0.0.1:8787 (OPENPRESENT_COLLAB_BIND to change it)

Open http://127.0.0.1:8787/editor.html, choose Share, and open the link in a second window. The server has no sign-in yet: the room key in the link is the only capability, so keep it on a trusted network (COL-03).

Desktop. desktop/ is a Tauri app around the same editor. CI bundles it for Linux, macOS and Windows on every push (desktop.yml, artifacts on the run); to build locally, build webapp/pkg as above, then cargo install tauri-cli --version "^2.0.0" --locked and cargo tauri build in desktop/.

How it is built

 Host (browser, desktop, collaboration server)
   └─ casual-slide-wasm: the bridge the editor's worker calls
        ├─ Operations, undo, co-editing wire                   casual-slide-transaction
        ├─ Inheritance resolver, geometry, text layout          casual-slide-style, -geometry, -text
        └─ Render backends: PNG and PDF                         casual-slide-render
   Import and export                                            casual-slide-package, -ooxml, -import, -export, -model

Each layer depends only on the layers below it, and the engine has no network capability at all. The architecture explains what is shared with OpenCalc and what had to be different; docs/19 has the crate graph as built.

| Crate | What it does today | | --- | --- | | casual-slide-package | Bounded ZIP and OPC admission: size, ratio and entry limits, safe part names, salvage, raw-copy rewriting | | casual-slide-ooxml | Part graph, the single bounded XML reader, a byte-faithful XML tree, markup compatibility, recovery and repair | | casual-slide-model | The presentation as plain typed values | | casual-slide-import, -export | XML to model, and model changes patched back into XML by the one writer | | casual-slide-geometry | Preset and custom shape geometry, deterministic on every platform | | casual-slide-style | Effective properties through the master, layout and theme chain, resolved at read time | | casual-slide-text | Fonts, shaping, line breaking and paragraph layout into glyph runs; caret stops | | casual-slide-render | Slides to PNG and PDF: shapes, text, pictures, tables, charts, effects | | casual-slide-transaction | Edit operations with exact inverses, undo history, and the co-editing seam | | casual-slide-wasm | The browser bridge: open, draw, edit, save, export | | server/casual-slide-collab-server | Orders and relays co-editing operations; holds no model (its own workspace) | | desktop/ | The Tauri desktop app around webapp/ (its own workspace) |

Documentation

| Read | For | | --- | --- | | docs/00 | The index of every design document | | Roadmap | Phases, tiers, and their exit criteria | | Security threat model | Every threat, its control, and its test | | Spec checklist | Every tag, property and value in the format | | Fidelity | How fidelity is measured | | PowerPoint fit-gap | All 352 features, our plan for each, and the parity audit of the editor today | | Changelog | What landed, by date |

Contributing

The project is designed before it is built, and every change follows one cycle: design, build, run it, look for what is wrong, fix it, with a test that fails without the fix. AGENTS.md is the contract and CLAUDE.md the working rules, for people and coding agents alike. Commits follow Conventional Commits and cite a tracker row.

Run the gates before committing:

cargo fmt --all -- --check
cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
cargo test --workspace --all-features --locked
RUSTDOCFLAGS="-D warnings" cargo doc --workspace --all-features --no-deps --locked
cargo check --target wasm32-unknown-unknown --workspace --locked
python3 tools/check-repo.py

The full list, exactly as CI runs it, is in CLAUDE.md.

Found a security issue? Please report it privately to the maintainers rather than in a public issue.

License

Apache-2.0. The vendored Office Open XML schemas are © Ecma International and Microsoft and are used under their published terms; see schemas/README.md.

PowerPoint and Microsoft Office are trademarks of Microsoft Corporation. OpenPresent is not affiliated with or endorsed by Microsoft.