platform:  macOS, Apple silicon
version:   1.0.2
licence:   one person, up to 3 Macs
price:     $19.99 introductory, $24.99 after

You edit the rendered document.

Most of the writing around code is Markdown. The README, the ADRs, the runbook you wrote after breaking the same release twice. Heron renders all of it in the pane you are typing in, on the plain files already sitting in your repo.

Heron with a folder open. A file tree of a developer journal runs down the left with coloured dots beside three files, and the document pane on the right shows a release checklist with Warning, Caution and Note callouts in colour above a syntax-highlighted TOML block — Those three callouts are `> [!WARNING]`, `> [!CAUTION]` and `> [!NOTE]` in the file. GitHub will draw them the same way.

The reasonable worry about a WYSIWYG Markdown editor is that it will be fine right up until the document gets interesting. Bold, italic, bullet lists, sure. Then you paste in a Mermaid diagram and get a grey box with the word mermaid sitting on top of it.

What you type, and what you get

Every one of these renders in place as you type it, and goes back to the file as the plain text it came from.

You write	Heron shows
`\| a \| b \|`	A table. Tab between cells, drag a column border, set alignment; the alignment survives the save.
```mermaid	The diagram, drawn.
```toml, ```bash, …	Code, highlighted for that language.
`> [!WARNING]`	A GitHub-style callout in colour. Note, Tip, Important, Warning, and Caution.
`- [ ] ship it`	A checkbox you can click, which saves back as `- [x]`.
`$$ … $$`	Typeset math, inline in a sentence or set on its own line.
`[^1]`	A numbered footnote, linked to its definition at the foot of the document.
YAML frontmatter	A metadata block above the document, kept out of the prose.
`![](diagram.png)`	The image.
Blockquotes, nested lists, rules	What GitHub would do with them.

Six of them, in the app.

A vertical Mermaid flowchart rendered as a connected diagram in Heron, under the heading The pipeline, its first three nodes reading Bump version in Cargo.toml, Update CHANGELOG and a Tests green? decision — A ```mermaid fence, drawn here and left in the file as a fence, so GitHub still draws its own.

A four-column Markdown table rendered as a table in Heron, listing books by title and author with a centred star rating and a one-line take on each — Edited as a table, saved back as pipes and dashes with the column alignment intact.

Syntax-highlighted code blocks in a Heron document: a TOML package block showing a version line removed and re-added, and a shell block running git status, git tag and git push — The fence's language tag picks the colours. Nothing inside the block is touched on the way back to disk.

A checklist in a Heron document called overview.md, four boxes ticked in ochre and three left empty, above a short prose section — Click a box and that line becomes `- [x]` on disk. Nothing else moves.

A Heron document about Little's Law showing a typeset equation on its own line, a second worked equation with units, and inline mathematical symbols inside the surrounding sentences — Written as LaTeX between dollar signs, typeset by KaTeX, and stored as the LaTeX you typed.

The top of a Heron document showing a frontmatter block of project, kind, updated and tags keys set apart in a tinted plate, above the document's title and opening paragraph — Frontmatter is set as a plate rather than parsed away, and it saves back exactly as you wrote it.

Your folder, your files

Heron opens a folder and shows you every .md file underneath it. No library and no format of its own.2 Point it at a repo, edit README.md and everything in docs/, then commit the way you always did.

A document you write in Heron looks like this on disk:

# Release checklist

> [!WARNING]
> Tag the release before the binaries go out.

- [x] Bump the version
- [ ] Notarise the DMG

| Step | Owner |
| ---- | ----- |
| Tag  | James |

Open it in vim, diff it, or hand it to whatever generates your docs site.1

It works across the whole folder

Heron watches the whole folder you opened: what you have changed anywhere inside it, what changed under you while you were elsewhere, and any file you want next, a couple of keystrokes away.

Heron's file sidebar showing an ochre dot beside two modified files and a green dot beside an untracked one — **Git status in the sidebar.** Ochre means modified, green means untracked. It is your actual Git status, read from your own repository, refreshed when you come back to the window.

Heron's quick-open palette over a dimmed document: the query rlch has matched release-checklist.md and latency-math.md, with the matched letters highlighted and a two results count at the foot of the panel — **Quick open.** `⌘T`, then `rlch`. The letters have to be in order, not next to each other, and it looks at every file in the folder rather than only the ones on screen.

Find and replace runs across every file in the folder at once, so renaming something everywhere is one operation rather than forty. A file edited outside Heron reloads in place while you watch it happen.

Two documents at once

Split the window and each side keeps its own tabs, its own scroll position, and its own file.

Heron split into two panes, a standup log rendered on the left and a weekly plan on the right, each pane with its own tab bar — A standup log on the left, the week's plan on the right, both rendered and both editable.

The rest of the editor is what you would expect one to have: tabs, an outline of the current document, word count, native macOS spellcheck, Print or Save as PDF, and Copy as Rich Text for the email where Markdown will not survive.

Eleven themes

A theme sets the typeface and the line width as well as the colour. You are picking paper, not a palette. Eleven ship, in light and dark. Here is one file in six of them.

Heron's house theme, Shallows. A note about Rust ownership set in Source Serif headings over an Inter body, slate on warm grey paper — Shallows

The same note reset in Manuscript, serif throughout: Playfair Display headings above a Lora body, on cream — Manuscript

Dusk sets the note in Cormorant Garamond headings over an EB Garamond body, on a cool violet-tinted paper — Dusk

Ember is the one sans-serif heading among these six. Bricolage Grotesque over a Literata body, on warm paper — Ember

The house theme inverted. The same Source Serif headings and Inter body, now pale on a deep slate ground — Shallows Dark

Quill Dark sets the note in Fraunces on near-black, with a rounded Quicksand body beneath it — Quill Dark

What it costs

$19.99 introductory, $24.99 after3

One payment. One licence for one person, on up to three Macs. Every 1.x update included. Nothing to renew, nothing to cancel, and no plan to move any of this behind a subscription.

Buy Heron for macOS Download the 14-day trial

The trial is the whole app for fourteen days, not a cut-down version of it, and it does not ask you to make an account.

Details

Your files: Plain .md files in a folder you choose. Heron edits them where they already are.
Account: None.
Support: Through the contact form. We aim to reply within two business days.

1: There is an escape hatch, per tab. A </> button at the end of the tab bar flips the current document to its raw Markdown and back, for the handful of things you would rather type by hand. ↩
2: Heron does not sign you in, sync anything, or send your documents anywhere. ↩
3: $19.99 is the introductory price and it becomes $24.99 when the introductory period ends. Buy at either price and the 1.x updates are included the same way. ↩