Gamma API PPTX export quality: developer test guide

Gamma's Generate API is the stronger choice when the product needs prompt-to-polished presentation creation, a collaborative web editor, and Gamma's theme system. Its current PowerPoint export embeds theme fonts, but Gamma also documents fallback rendering for some visual effects and static-image export for infographics. Runstamp is aimed at a different job: generating a constrained, native Office artifact from structured data, with explicit validation, local execution, and commercial deployment terms.

“PPTX export” is not one quality metric

Teams testing the Gamma Generate API often ask whether its PowerPoint export is “good.” That question hides at least four tests:

1. Visual fidelity: does the exported slide resemble Gamma's Present Mode?
2. Native editability: can a recipient edit text, shapes, and chart data as PowerPoint objects?
3. Brand control: can the system repeat the customer's fonts, colors, logos, and layouts?
4. Infrastructure fit: can the generation path meet deployment, privacy, and product-embedding requirements?

A tool can be excellent at first-draft design and still be the wrong infrastructure for a customer-facing native deliverable. Conversely, a structured document engine can produce highly editable files while offering nothing comparable to Gamma's interactive authoring experience.

Methodology and date: Gamma details below are based on Gamma's public developer docs, help center, and terms as of July 19, 2026. No private Gamma account or undocumented feature was used. Runstamp details are based on its live fixture, package documentation, and current pricing terms. Runstamp is our product.

Gamma API vs Runstamp

What Gamma's current docs say about PPTX fidelity

Gamma's v1 developer documentation lets a generation request set exportAs: "pptx", then returns a signed export URL after the job completes. The API became generally available in November 2025.

The current Gamma export guide makes several concrete claims worth using instead of anecdotes:

• PowerPoint exports match Present Mode, not Gamma's Edit Mode.
• Gamma embeds the theme's heading and body fonts, including uploaded custom fonts and bold weights, in the PPTX.
• A font can still fall back if it cannot be fetched during export, and the application opening the file must support embedded fonts.
• Gradient headings, custom accent-image shapes, and frosted backgrounds can render differently or use fallback styles because the target formats do not support every Gamma effect.
• True italic font files are not embedded in every case; italic can use a slanted regular font.

That is not evidence that Gamma's export is poor. It is evidence that Gamma is converting a richer card-based presentation surface into PowerPoint, and that some web-native effects have no exact PowerPoint equivalent.

Native editability needs its own test. Gamma's help center says AI infographics export to PowerPoint as static images. The public documentation reviewed does not state that every chart, diagram, or smart layout becomes a native PowerPoint object with editable underlying data. If editable chart series are a contract requirement, inspect the actual exported object rather than inferring it from the .pptx extension.

Gamma has real brand controls

It would be inaccurate to describe Gamma as brand-blind. Gamma supports workspace themes, custom colors, custom fonts, logos, accent images, and theme sharing. Its theme documentation says a team can import a PowerPoint or Google Slides theme and extract colors, fonts, and logos. The v1 API exposes themes, and the developer docs include a generate-from-template endpoint.

The distinction is ownership and enforcement:

• Gamma owns a strong visual theme and editor workflow, then exports to PPTX.
• Runstamp treats structured content and native artifact generation as the primary workflow. Local documents can carry explicit style tokens, while Platform adds managed preflight and delivery controls.

Pro covers support for local deployments and does not include managed API access. Gamma remains the more direct choice when designers need to build and refine themes in a visual application; Runstamp is designed for software products that generate structured, native documents through code.

Deployment and embedding rights need precise language

Gamma's documented API endpoint is a managed cloud service at public-api.gamma.app. I did not find a self-hosted or customer-VPC option in the public API documentation reviewed for this article. That is not proof that Gamma will never negotiate a private arrangement; teams with that requirement should ask Gamma directly and get the deployment boundary into the contract.

Runstamp's local packages and MCP server can run in the application's own environment. Their Apache-2.0 licenses grant commercial use without an Enterprise agreement. Pricing offers company-wide production support under Pro and managed processing and workflow controls under Platform. Enterprise can add negotiated OEM terms for identified commercial components and services, volume, security review, and service terms.

Gamma's public terms are also more permissive than a simplistic “no embedding” claim. They grant a limited right to use the API to develop an application under the customer's branding and to display applications to appropriate end users, subject to the agreement. Runstamp uses different packaging: Apache-2.0 components retain their license rights, Platform includes managed processing, and Enterprise addresses separately identified commercial components and services.

This is a product comparison, not legal advice. If generated presentations are embedded in a paid product, have counsel review the current contract for the exact distribution model.

Run a live native-PPTX fixture

The Runstamp PPTX output record explains the current format boundary and links to the structured evaluation payload. The fixture includes native bar and line charts with embedded Excel data, text, shapes, pricing cards, and team content.

Download the current artifact from the output record, or reproduce it locally with @runstamp/pptx. The historical showcase compiler is not the supported managed API contract; free-trial workspaces and active Platform and Enterprise workspaces use the hosted quick start.

In the showcase output, open the deck in PowerPoint, select a chart, choose Edit Data, change a series value, and confirm that the chart updates. That is a more useful editability test than comparing thumbnails.

A fair PPTX export test for both tools

Use the same real customer content and score the outputs separately on visual quality and object structure:

1. Set a fixed 16:9 page/card size before generation.
2. Use the actual brand fonts, including bold and italic text.
3. Include a long title, a dense table, one chart, one diagram, and one image treatment.
4. Compare Gamma's exported file with its Present Mode, not Edit Mode.
5. In PowerPoint, edit every text block that a recipient is expected to change.
6. Open chart data and change a series value; record whether the chart is native, grouped shapes, or an image.
7. Reopen the file on a second machine or Office environment to catch font fallback.
8. Repeat the same API input several times if deterministic layout matters to downstream review or visual diffing.

Do not collapse these results into one “quality” score. A beautiful but partially flattened deck may be perfect for presenting and wrong for a client handoff. A fully native deck may be operationally ideal and still need stronger art direction.

When Gamma is the better choice

Choose Gamma when:

• the user wants to go from a prompt to a visually polished first draft quickly;
• a collaborative web editor and AI-assisted refinement are core product value;
• presentations, websites, social posts, and visually rich documents belong in the same creative workflow;
• workspace themes and a designer-friendly theme editor matter more than code-owned layout; or
• PowerPoint is a downstream export, not the canonical artifact contract.

Gamma is a mature end-user creation product. Runstamp does not try to replace its editor.

When Runstamp is the better choice

Choose Runstamp when:

• the canonical input is structured application data rather than a prose prompt;
• recipients must edit native text, shapes, tables, or chart data in Office;
• validation findings need to participate in an automated approval workflow;
• generation must run locally or through the authenticated Managed API; or
• the commercial product needs explicit embedding or OEM terms across native Office formats.

Runstamp requires developers to own document structure and art direction. Gamma is usually better for one-off creative authoring; Runstamp is designed for recurring document infrastructure, with managed brand ingestion, preflight, approvals, webhooks, and audit evidence on Platform.