Saving & Round-tripping

handler.save(slides, options?) serializes your (possibly edited) slides back into a valid .pptx ZIP archive and returns a Uint8Array.

const bytes = await handler.save(data.slides); // => Uint8Array

Use the originating handler

Call save() on the handler that loaded or created the data. It holds the in-memory ZIP - media, masters, themes, custom XML parts, VBA - that the save pipeline reuses for anything you didn't touch.

What the save pipeline rebuilds

When you call save(), the runtime:

1. Reconciles the slide list - added, removed, and reordered slides - and updates ppt/presentation.xml.
2. For each slide, rebuilds the shape tree from element data: serializes text paragraphs and run properties, writes shape styles, effects, and transforms, updates relationships (images, charts, media), writes animation timing trees, and updates notes.
3. Rebuilds [Content_Types].xml and writes document properties and comments.
4. Preserves VBA macros and custom XML parts that the model doesn't represent.
5. Generates the ZIP with DEFLATE compression and returns the bytes.

Round-trip safety

The engine is built for full round-trips: load a deck, edit a fraction of it, save, and everything you didn't touch passes through verbatim. Unmodelled parts (macros, custom XML, masters/layouts you didn't change) are carried forward from the loaded archive rather than regenerated.

OOXML Strict ↔ Transitional normalization

Office 365 can save files in ISO/IEC 29500 Strict mode, which uses different namespace URIs than the common Transitional (ECMA-376) format. On load the engine maps 46+ namespace URI pairs (Strict → Transitional); on save it converts back. This is automatic.

WARNING

Features that rely on strict-only extensions outside the mapped namespace set may not round-trip. See /guide/limitations.

Save options

save(slides, options?) accepts a PptxHandlerSaveOptions object for persisting parts that live outside the per-slide element model - for example:

Option	Purpose
coreProperties / appProperties / customProperties	Document metadata.
sections	Slide section grouping.
customShows	Custom slide-show definitions.
presentationProperties	Show type, loop, etc.
slideMasters / slideLayouts	Typed mutations to masters/layouts (clrMap, background, hf flags). Anything not listed passes through verbatim.
headerFooter, notesMaster, handoutMaster, viewProperties, tags, modifyVerifier	Other presentation-level parts.

const bytes = await handler.save(data.slides, {
	coreProperties: { ...data.coreProperties, title: 'Final Report' },
	sections: data.sections,
});

Writing the result

Node fs

import { writeFile } from 'node:fs/promises';

const bytes = await handler.save(data.slides);
await writeFile('output.pptx', bytes);

Browser download

const bytes = await handler.save(data.slides);
const blob = new Blob([bytes], {
	type: 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
});
const url = URL.createObjectURL(blob);
const a = document.createElement('a');
a.href = url;
a.download = 'output.pptx';
a.click();
URL.revokeObjectURL(url);

Exporting individual slides

To export selected slides as standalone .pptx files:

const exports = await handler.exportSlides(data.slides, { slideIndexes: [0, 2] });
// => Map<number, Uint8Array> keyed by slide index

Saving encrypted output

To write a password-protected file, use saveEncrypted instead of save:

const bytes = await handler.saveEncrypted(data.slides, 'secret');
// => Uint8Array of an encrypted OLE2 package

See /core/encryption for algorithm options and details.