FoldRender / Guides / Mermaid diagrams and LaTeX math, rendered on your phone
FoldRender guide
Mermaid diagrams and LaTeX math, rendered on your phone
Architecture diagrams and equations are the part of a README that usually degrades to quoted source on a phone. FoldRender renders them, from assets bundled inside the APK, with the rendering surface cut off from the network entirely. Here is how to get them on screen and how to confirm for yourself that nothing is being fetched.
FoldRender is on the Play Store as FoldRender: Git Repo Reader, package id dev.foldrender.app, free and distributed worldwide. Install it the ordinary way — no allow installs from this source prompt to approve, and updates arrive on their own. The app declares minSdk 30, so it needs Android 11 or newer; Play will tell you if a device is below that rather than letting you install a build that cannot run.
Open a document that contains them
Clone the repository from the git panel, or use Open a file / Open a folder for something already on the phone. Then tap the Markdown file in the Files tab. Nothing has to be enabled: mermaid and math are part of the Markdown pipeline, not a setting.
Write the fences the way you already do
A diagram is a fenced block tagged mermaid. Math is $…$ inline and $$…$$ as a block. These are the same conventions GitHub and Obsidian use, so an existing README needs no changes to render here.
Tap a diagram that is too dense to read
Tapping a rendered diagram opens it full-screen with pinch zoom, which is the only way a wide sequence diagram is readable on a folded phone. A close control returns you to the document at the same scroll position.
Prove it is offline
Turn on airplane mode and reopen the document. The diagrams and equations still render. This is not a cache: mermaid and KaTeX, fonts included, are packaged in the APK's assets, the rendering WebView has blockNetworkLoads set, and its client returns a 403 for any URL that is not a bundled asset or a data URI. There is no configuration that would let it reach the network.
Export with the diagrams intact
Export or share in the ⋮ menu opens the Export sheet. Share as HTML writes one self-contained file with the KaTeX fonts, the mermaid output and every image inlined as data URIs — it opens on a machine that has never heard of mermaid. Print / Save as PDF and Share as PNG come from the same HTML, so all three match what was on screen.
How FoldRender handles it
One island per block, not one WebView per app
Each math or diagram block gets its own sandboxed rendering island rather than the whole document being handed to a browser. The prose around it stays native Compose — native text selection, native theming, native scrolling.
Blocked twice over
Network access is refused by the WebView client, which returns a 403 for anything outside the bundled asset directory or a data URI, and independently by blockNetworkLoads on the WebView's settings. Either alone would do it; both is the point.
Inside real documents
Diagrams and math sit in the same GFM Markdown the app already renders — tables with alignment, task lists, callouts written as > [!NOTE], footnotes, wiki links and front matter as a metadata header.
What does FoldRender not do?
The honest list — shipped-but-unverified behaviour included, so you can tell before installing whether this build does the thing you came for.
What this page says about the current app was read from its source on 2 November 2026. The same day, the then-current release, built from its tag, was walked signed out on two cloud phones (Galaxy S26 on Android 16, Pixel 9 on Android 15): it cloned a public repository, edited and saved a file, made a local commit with push off, and opened 16 file types, none of them source code. Not part of that run, among other things: push, Sign in with GitHub in the browser, cloning a private repository, PDF search and passwords, HTML find, export, deleting a clone, the diff viewer, and fold and unfold on real hardware. Clean-device results on this page are from an earlier pass, on an earlier build.
Mermaid is the only diagram engine bundled. Graphviz and PlantUML are not included, because each additional engine is megabytes of JavaScript in the APK for a syntax fewer design docs use.
Diagram bitmaps are not cached across scrolls. Scroll a long way past a diagram and back, and it re-renders; off-screen blocks are simply not composed, which is the cheaper half of the same trade.
The clean-device verification pass covered Markdown, source code, PDF and notebook rendering. The diagram and math island is described here from the shipped implementation — bundled assets, blocked network — rather than from a separate hardware test of every diagram type.
There is no diagram editor. FoldRender renders the fence you wrote elsewhere.
How does FoldRender compare with the other ways to read a repo on Android?
Four apps people actually reach for, and the one axis that separates them: whether the repository ends up on the phone, and whether anything renders it once it is there.
Prices are for the download. GitHub Mobile’s capabilities follow your GitHub plan; Termux and MGit are both free software. MGit’s version and date are from its F-Droid listing.
What are the numbers behind FoldRender?
Every figure here is read out of the shipping build or off a primary source listed at the foot of this page — nothing is rounded up for effect.
Price: US$0 on Google Play, distributed worldwide. There is no billing library in the build, no subscription and no paid tier to upgrade to.
Current release: the version the Google Play listing shows. This page does not repeat the number, which would be wrong between a release and the next site update. The app's figures here were last checked against its source on 2 November 2026.
Android floor:minSdk 30 — the API level Android 11 shipped with in 2020 — compiled and targeted against API 36.
Highlighting: 65 languages recognised across 89 file extensions, applied lexically to the whole file.
Reading limits: a single file is read up to 32 MB and then flagged truncated; workspace grep skips files over 1.5 MB and stops after 500 matches rather than flooding the pane.
Reference device: the Galaxy Z Fold 7, launched in 2025 — an 8-inch inner screen, 8.9 mm folded, and a 4,400 mAh battery Samsung rates at up to 24 hours of video playback.
The lineage: Git has been public since 2005, so the on-disk format this app reads is 21 years old; Samsung shipped the first Galaxy Fold in 2019, giving Android 7 years of real foldable hardware to target.
The toolkit: the UI is Jetpack Compose, whose 1.0 shipped in 2021, on an OS that has had split-screen multi-window since 2016.
FAQ
Does FoldRender render mermaid and LaTeX on Android?
Yes. Mermaid fenced blocks and $…$ / $$…$$ math embedded in Markdown render through an island backed by mermaid and KaTeX bundled inside the APK, alongside the tables, task lists and callouts of ordinary GFM.
Do diagrams need an internet connection?
No, and it is enforced rather than merely unnecessary: the rendering WebView has network loads blocked and its client refuses any request that is not a bundled asset or a data URI. Airplane mode changes nothing about how a document renders.
Can I zoom into a diagram?
Yes. Tapping a diagram opens it full-screen with pinch zoom, which is what makes a wide flowchart usable on a folded phone.
Will an export keep the diagrams?
Yes. Share as HTML inlines the KaTeX fonts, the mermaid output and the images as data URIs into one file, so it renders on a machine with no toolchain. PDF and PNG export come from the same HTML.
What about Graphviz or PlantUML?
Not bundled. Mermaid covers the diagrams that actually appear in design docs, and every extra engine is megabytes of JavaScript shipped to every user.
Which math delimiters work?
Inline $…$ and block $$…$$ — the delimiters GitHub and Obsidian already use, so documents written for those render here without editing.
How much does FoldRender cost?
US$0. It is free on Google Play, distributed worldwide, with no billing library in the build, no subscription and no paid tier.
Which Android versions does FoldRender run on?
Android 11 and newer. The app declares minSdk 30 — the API level Android 11 shipped with in 2020 — and is compiled and targeted against API 36. It is developed and tested on a Galaxy Z Fold 7, which launched in 2025.
Does FoldRender work offline?
Yes, once a repository is on the device. Cloning needs the network; reading, searching, and rendering Markdown, source, PDFs and notebooks out of a clone or a picked folder do not. Signing in to GitHub is optional and only matters for private repositories.
How is this different from GitHub Mobile, Termux or MGit?
GitHub Mobile reads repositories hosted on GitHub and does not clone to the phone. Termux and MGit both clone and then leave rendering to you — Termux gives you a shell, MGit ships no text editor at all. FoldRender clones over HTTPS and renders what it clones, on the inner screen.
Where can I check these claims?
The primary documents behind the figures above, so you can confirm any of them without taking our word for it.