Show HN: Slidown – Markdown to PowerPoint in pure Go, no AI in generation

Slidown, a pure-Go tool for converting Markdown to PowerPoint files without AI, has been released as an open-source sibling to the deck Google Slides tool. It writes standalone .pptx files via a native OOXML writer, supports in-place updates that preserve manual edits, and offers watch mode for automatic rebuilds. The tool is designed to work interchangeably with deck from the same Markdown source.

slidown is a tool for creating PowerPoint .pptx presentations from Markdown. It is a sibling project of k1LoW/deck https://github.com/k1LoW/deck , a Markdown → Google Slides tool by @k1LoW https://github.com/k1LoW . slidown shares deck 's philosophy of Markdown for content, slide tooling for design , and adopts the same Markdown format and element mapping. The difference is the output target: slidown writes standalone .pptx files via a pure-Go OOXML writer, with no third-party Office dependencies. deck and slidown are designed to be used together or interchangeably from the same Markdown source, so you can pick the right delivery target — Google Slides or PowerPoint — without rewriting your slides. Homebrew: bash $ brew install Songmu/tap/slidown go install: bash $ go install github.com/Songmu/slidown/cmd/slidown@latest Write your slides in Markdown: --- title: Talk about slidown --- First slide A subtitle - a bullet point - bold and italic and code - a nested point --- Second slide A paragraph with a link https://example.com . Then apply it to a .pptx : bash $ slidown apply deck.md Wrote deck.pptx 2 slide s By default the output file is the input file name with a .pptx extension. Override it with --output / -o , or with the output frontmatter field: bash $ slidown apply deck.md -o talk.pptx If the output .pptx already exists, apply updates it in place. Slides whose source content has not changed keep their existing slide parts verbatim, so manual edits made in PowerPoint to unchanged slides are preserved; only changed slides are regenerated: bash $ slidown apply deck.md -o deck.pptx Updated deck.pptx 2 slide s Image-only differences recompression, reordering or repositioning are treated as unchanged, so adjusting images in PowerPoint does not trigger a regenerate. To make reuse robust against page reordering, give a page a stable key — otherwise pages are matched by position: php Overview < -- {"key": "overview"} -- A page can also be frozen with the freeze page configuration. A frozen page keeps its existing slide as-is on rebuild even if its Markdown changed — useful for pinning a slide you have hand-tuned in PowerPoint: php Hand-tuned slide < -- {"freeze": true} -- To bring in a slide pasted from another presentation , declare a keyed, frozen placeholder page for it in the Markdown and paste the slide at that position in PowerPoint: php Imported slide < -- {"key": "imported-architecture", "freeze": true} -- On rebuild, apply pairs the placeholder with the pasted slide by position, keeps the pasted slide verbatim freeze , and stamps the key onto it — so later rebuilds match it by key even after reordering. The deck source is authoritative for keys: a key renamed or removed in the Markdown is updated or cleared on the slide accordingly, and freeze: true need only stay in the Markdown. Use --watch or -w to keep apply running and automatically re-apply when the deck markdown file changes: bash $ slidown apply deck.md --watch Wrote deck.pptx 2 slide s Updated deck.pptx 2 slide s slidown watches the deck file's directory so editor atomic-save patterns rename / remove + create are handled, filters events to the deck file, and debounces bursts so one save triggers one rebuild. If a rebuild fails, the error is printed and watch mode keeps running until you stop it with Ctrl-C . --watch and --template are mutually exclusive. --template is only for initial generation; when you need watch mode with a template, set template in the config file instead. MVP scope: watch mode currently tracks deck markdown file changes only. Supply a .pptx or .potx whose theme, slide masters and layouts should be used as the design when creating a new output file: bash $ slidown apply deck.md --template theme.pptx A template can only be supplied when the output file does not yet exist. It may also be set with the template config field. When the output already exists it is updated in place, reusing itself as the template, and passing --template is an error choose a different --output , or remove the file first . See docs/templates.md /Songmu/slidown/blob/main/docs/templates.md for layout selection, inspecting available layouts with ls-layouts , and repurposing existing placeholders as subtitle targets. Templates can also include a style layout /Songmu/slidown/blob/main/docs/templates.md style-layout to customize inline syntax and table styling. Incremental updates reuse unchanged slides from the existing output file and still honor freeze: true .The Markdown used by slidown consists of an optional YAML frontmatter and a body. Slides are separated by a line of three or more hyphens --- . --- title: Talk about slidown output: talk.pptx --- First Slide Content... title string : The title of the presentation, written to the generated .pptx document properties metadata . output string : Output .pptx path used when --output is not given . breaks boolean : Control how single line breaks are rendered. Default false renders them as spaces; true preserves them as line breaks. codeBlockToImageCommand string : Command used to convert code blocks to images see Code blocks to images code-blocks-to-images . defaults array : Conditional page configuration using CEL expressions. slidown follows the same Markdown specification as deck : CommonMark plus selected GitHub Flavored Markdown extensions tables, strikethrough , with a restricted set of raw inline HTML for text-level semantics <mark , <kbd , <sub , <sup , <u , … . Speaker notes are written as HTML comments < -- ... -- . Within each slide, headings are mapped to placeholders by depth: - The shallowest heading on the slide → title - The next heading level → subtitle - Everything else → body See docs/markdown.md /Songmu/slidown/blob/main/docs/markdown.md for the full Markdown reference, including supported/unsupported features, inline-style mappings and line-break handling. A few edge behaviors notably how content that overflows the available placeholders is handled currently differ from deck and are not yet a stable contract; these are called out inline in that reference. slidown reads optional global configuration: ${XDG CONFIG HOME:-~/.config}/slidown/config-{profile}.yml with --profile ${XDG CONFIG HOME:-~/.config}/slidown/config.yml breaks: true codeBlockToImageCommand: "go run ./cmd/txt2img" template: "theme.pptx" Settings in frontmatter take precedence over the configuration file. The template field is honored only from the configuration file or the --template flag and only when creating a new output file; it cannot be set in a deck's frontmatter. You can convert Markdown code blocks to images by specifying a command that outputs image data PNG/JPEG/GIF to standard output, or to a file via the {{output}} placeholder: bash $ slidown apply deck.md --code-block-to-image-command "some-command" This is useful for rendering diagrams e.g. Mermaid or syntax-highlighted code as images. slidown is under active development. apply already reuses unchanged whole slides; finer-grained intra-slide sub-element diffing is future work. See docs/design.md /Songmu/slidown/blob/main/docs/design.md for the architecture and the incremental-rebuild design. — k1LoW/deck slidown is a sibling project of deck and reuses its Markdown parsing and content model. The Markdown specification, the element-to-slide mapping rules and much of the surrounding design come from deck . Many thanks to @k1LoW https://github.com/k1LoW and the deck contributors.