Jayson vs MermaidEditor
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Jayson
This app allows you to view and edit JSON files directly on your device. It offers features like tabbed browsing, split-screen comparisons, and integration with Siri Shortcuts and the Share Sheet for easy JSON parsing and management.
- Browse JSON files
- Table or syntax highlighted text view
- Tabbed interface
- Multiple splits for comparison
- Siri Shortcuts integration
- Share Sheet Actions
- URL schemes
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Jayson is a JSON viewer and editor for iPhone and iPad. Browse JSON as a structure, edit values, and save your changes back to the file. Whether you're inspecting an API response, checking a config file, or making a quick fix on the go, Jayson turns raw JSON into something you can actually read and change. BROWSE AND EDIT - Open JSON files stored on your device or in iCloud Drive. - Toggle between a structured table view and syntax highlighted text. - Add new values and keys, and save your changes back to the file. - Parse text or the contents of a URL from your clipboard into JSON. - Highlight a key from a child of an array to get a quick overview of your data. TABS, SPLITS, AND WINDOWS - Switch between files, or different objects in a single file, using tabs. - Compare JSON in a single file or across files using multiple splits. - Open multiple windows on the iPad. WORKS WITH SHORTCUTS Jayson integrates with Shortcuts, which comes in handy for debugging API calls, previewing JSON files, and building workflows around JSON. - Pass a response from Get Contents of URL to Jayson to see how it is structured. - Open JSON as a document you keep working on, or as a temporary preview. - Format JSON and hand the result to the next action, using spaces or tabs. FREE, WITH AN OPTIONAL UPGRADE Jayson's core functionality is free. Browsing, editing, saving, splits, Shortcuts, and working with up to two tabs at a time cost nothing. A one-time in-app purchase enables having more than two tabs open at once, switching between light and dark themes, and personalizing the app icon, accent color and type icons. One purchase, no subscription.
MermaidEditor
Create and edit diagrams and charts using mermaid-js syntax with real-time preview. Export your creations as PNG or SVG files and share them across all your Apple devices.
- Mermaid-js syntax highlighting
- Code completion
- Instant preview
- Export to PNG/SVG
- Cross-device editing
- QuickLook preview extension
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MermaidEditor is a diagram and chart editor, powered by mermaid-js. And MermaidEditor supports iPhone, iPad and Mac, with one app you can edit diagram everywhere on any device. MermaidEditor supports mermaid-js syntax highlighting and code completion, so it can help writing diagram and chart clearly, easily and quickly. You can also easily export charts as PNG images or SVG files from the editor, or share image to other people with system actions. √ All Platforms - Both Mobile and Desktop platforms supported, you can edit diagram documents on iPhone, iPad or Mac - Document browser based app, easily edit files on device and sync document between devices - Multiple windows ready, it makes the editor more powerful on iPadOS - Keyboard shortcuts ready on iPadOS with keyboard connected √ Powerful Editor - Syntax Highlighting for mermaid-js grammar - Auto Completion in editor helps typing keywords quickly - Code Snippets likes parallel block in sequence diagram makes life easier - Instant Parsing Error indicator for locating syntax error √ Instant Preview - Auto Generated Preview when typing in editor - Zoom and Pan to move preview for checking diagram's detail - With Scroll wheel it can be easily zoom diagram on macOS √ Integrated Extensions - Thumbnail support, every .mmd file will has its own thumbnail when saving file - QuickLook Preview extension helps you preview mermaid document in Files app on iPhone or iPad and Finder on macOS √ Sharing - Save diagram document as its source with .mmd extension - Export diagram to PNG image or SVG file with one click For mermaid-js grammar, please visit https://mermaid-js.github.io/mermaid/ for documentation.
Screenshots
Verdict
The clearest difference is review sentiment: Jayson at 81% against MermaidEditor's 14%. Jayson also leads on price (Free vs $3.99) and rating (4.5 vs 2.3). MermaidEditor's advantage is in-app purchases (none vs 1) and device support (4 vs 2). On update cadence, ads and chart position there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Jayson is free to download; MermaidEditor costs $3.99 up front. Jayson sells 1 one-off in-app purchase. MermaidEditor asks for nothing beyond the download.
Jayson holds the better App Store score, 4.5 against 2.3. That said, the two scores are not equally well evidenced: Jayson has 425 ratings behind it against 10, so its average is the more settled of the two. Written reviews point the same way: 81% of Jayson's written reviews are positive against 14% of MermaidEditor's.
Both ship on a similar rhythm, roughly every 3 weeks. Both last shipped on October 17, 2026.
| Parameter | Jayson | MermaidEditor |
|---|---|---|
| Price | Free — better | $3.99 |
| Rating | 4.5 (425 ratings) — better | 2.3 (10 ratings) |
| Positive reviews | 80.7% of reviews — better | 13.8% of reviews |
| Number of ratings | 425 — better | 10 |
| Update frequency | Every 3 weeks | Every 3 weeks |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases — better | Paid |
| Best chart rank | #103 — better | #116 |
| Devices | iPhone, iPad | iPhone, iPad, iPod, Mac — better |
| Requires iOS | 26.0 | 14.0 — better |
| Further details — not scored | ||
| Size | 41 MB | 125 MB |
| Age rating | 4+ | 4+ |
| Developer | Simon B. Støvring | 基伟 徐 |
Customer experience
Jayson
MermaidEditor
Bugs and requests
Jayson
Reported bugs
6 issues- App crashes when opening large JSON files (89MB+)
- Crashes on regular use despite functionality
- Device freezing for extended periods
- Safari compatibility broken in recent updates
- Navigation back through JSON structure is unreliable
Show 1 moreShow fewer
- Accidental file exit when attempting to navigate
Requested features
9 requests- Search/find functionality within files
- JSON editing and modification capabilities
- XML format support
- Split-view for comparing different arrays
- Export functionality for edited JSON
Show 4 moreShow fewer
- Comment recognition in JSON files
- Plain text editor option
- Improved file size handling for large documents
- Better navigation controls on mobile devices
MermaidEditor
Not enough reviews yet to summarise bugs or requests.
In-app purchases
Jayson
- Unlock Everything$4.99
MermaidEditor
No in-app purchases









