Visual JSON

A Windows-first JSON editor built with VB.NET and WPF. Edit JSON as text or as a structured grid, view object arrays as an editable table, validate against JSON Schema, and convert to and from XML and YAML — with strict guarantees that saving and converting never corrupt your files.

日本語版は README.ja.md を参照してください。

Why Visual JSON

Feature	VS Code	Online JSON tools	Visual JSON
Local-only workflow	Yes	No	Yes
Grid editing	Extension-dependent	Limited	Built in
Table View	Limited	Limited	Built in
Schema diagnostic jump	Yes	Partial	Yes *
XML/YAML conversion preview	Partial	Partial	Built in
Pre-save validation / backup / recovery	Partial	No	Built in

* Schema validation covers a practical subset of JSON Schema keywords; allOf/anyOf/oneOf, $id, and remote $ref are not supported. See Limitations.

Sample Files

The samples/ folder is included so you can see the value quickly:

• api-response-invalid.json: open it with schema/user.schema.json to try schema diagnostics and click-to-jump.
• users-array.json: switch to Grid, open Table View, sort, and edit a scalar cell.
• config.jsonc: try JSONC comments, trailing commas, validation, and formatting.
• events.jsonl: open JSON Lines as an array-equivalent document and save back as line format.

Screenshots

Table View	Schema diagnostics

Highlights

• Fast text editing — AvalonEdit-based editor with line numbers, folding, search/replace (regex supported), and search highlighting. Rendering and syntax coloring are virtualized per visible line, so multi-MB documents stay responsive.
• Grid editing — valid JSON becomes a hierarchical tree with Key, Value, Type, and JSON Pointer columns. Add, delete, move, duplicate, retype, drag-and-drop (including across parents), and undo/redo structural edits.
• Table View — object arrays open as "row = element, column = property" for spreadsheet-style browsing, editing, and sorting.
• JSON Schema validation — a practical keyword subset including const, length limits, and same-document $ref, with diagnostics that jump to the exact body position.
• Safe conversion — JSON ⇔ XML and JSON ⇔ YAML with a mandatory preview; a cancelled or failed conversion never touches any file.
• English / Japanese UI — switch the entire UI, including the message pane and Table View, at runtime.

Features (v1.3.0)

Text editing

• Open and edit standard .json plus .jsonc, .json5, .jsonl, and .ndjson through the same workflow; unknown extensions are sniffed from content.
• Syntax validation after a 500 ms debounce with line/column diagnostics and click-to-jump.
• Folding, find/replace with optional regex and case sensitivity, search highlighting, and bracket/quote auto-pairing (toggleable).
• Key completion with Ctrl+Space: keys used by sibling objects in the same array plus schema properties, minus keys already present.
• Files with extremely long single lines (unformatted machine output) trigger an optional pretty-print prompt; declining opens the file unchanged.

Grid and Table View

• Hierarchical grid with JSON Pointer paths, filtering with parent context, and a row context menu (Add child / Add sibling / Delete / Move / Duplicate / Copy JSON Pointer / Jump to Text).
• Structural edits — including committed cell edits — register as single undo steps, with multi-step redo.
• Drag rows within a parent or to a different parent; key conflicts ask for confirmation and resolve with a unique key, and moving a node into its own descendants is rejected.
• Enter exactly {} or [] in a value cell to convert the node to an empty object or array.
• Table View for object-majority arrays (up to 10,000 rows; larger arrays warn and stay in the tree):
  • Missing properties display as empty cells; editing one creates the property on that row only.
  • + Row appends an empty object row; + Column adds a display column that materializes per edited row.
  • Column-header sorting is display-only until you press Apply to Structure (one undo step); the # column restores the structural order.
  • Container cells show read-only summaries ({…}, [n]); double-click to jump to that node in the tree.

JSON Schema validation

• Supported keywords: type, required, properties, additionalProperties, minimum, maximum, pattern, enum, array items, const, minLength/maxLength (counted in code points), and same-document $ref (#/...) with cycle detection and a depth limit of 32.
• format checks (date-time, date, time, email, uri) report warnings; unknown formats are ignored.
• Diagnostics carry JsonPath, JSON Pointer, body line/column, SchemaPath, and schema URI; click to jump to the body position or open the schema definition view at the failing keyword.
• External $schema fetching is off by default. When explicitly enabled, only HTTPS is allowed; redirects to HTTP, file:, UNC, localhost, and private/link-local ranges are blocked; hostnames are re-checked after DNS resolution (including IPv4-mapped IPv6) and connections are pinned to the validated addresses. External $ref URLs inside a schema are reported as warnings and never fetched.

Conversion

• Export JSON as XML (@name → attribute, #text → element text) or as YAML with 2-space indentation; open XML/YAML files as JSON documents.
• XML export options in the preview: arrays as repeated <item> elements (default) or repeated parent-name elements; null as an empty element (default) or xsi:nil="true". Options re-convert the preview instantly and always reset to the defaults.
• Every export shows a preview first; cancelling changes nothing, and a failed conversion never touches the original file.
• XML reading prohibits DTDs, external entities, and external subsets (XXE-safe).

File safety and environment

• Save As / overwrite saves validate strict JSON first, write through a temp file, and create a generation backup.
• JSON Lines documents save in line format (one compact JSON per line) while the editor displays the array-form standard JSON. Note: this changed in v1.2.0 — see RELEASE_NOTES.md for the compatibility details.
• UTF-8, UTF-8 BOM, UTF-16 LE, and UTF-16 BE are detected and preserved on save; CRLF/LF is preserved by majority detection.
• Recovery snapshots for unsaved edits, restorable on the next launch.
• Settings (language, window placement, backups, schema options, recent files) persist under %LocalAppData%\VisualJson\settings.json; broken settings are quarantined and defaults load.
• File logs under %LocalAppData%\VisualJson\logs never contain document or schema body content, and neither does the diagnostics copy.

Getting started

Download visual-json-v1.3.0-win-x64.zip, verify the SHA256 checksum shipped next to it, extract, and run VisualJson.App.exe. The package is self-contained — no .NET installation is required. The binary is unsigned, so SmartScreen may warn on first launch.

Building from source

Requires the .NET 10 SDK on Windows.

# Build
dotnet build VisualJson.slnx

# Run
dotnet run --project src\VisualJson.App\VisualJson.App.vbproj

# Test (MSTest)
dotnet test tests\VisualJson.Tests\VisualJson.Tests.vbproj

# Package (outputs zip + sha256 under artifacts/)
.\scripts\package-windows-x64.ps1

Limitations (v1.3.0)

• JSONC / JSON5 input is normalized to standard JSON for parsing. Comments are not preserved after formatting, grid sync, save, or conversion (best effort by design).
• JSON5 support covers representative syntax (comments, single-quoted strings, unquoted keys, trailing commas), not the full JSON5 language.
• JSON Lines is treated as an array-equivalent document. Saving uses the line format and does not preserve blank lines or the original per-line formatting.
• Schema validation covers the keyword subset listed above. allOf/anyOf/oneOf, $id, remote $ref, and draft-specific behaviors are not supported.
• YAML to JSON covers a representative block-style subset. Anchors, aliases, tags, block scalars (|, >), and non-empty flow collections are rejected with a clear error.
• XML to JSON keeps values as strings by default.
• Files of 50 MB or larger open in text mode with full grid editing disabled for the session; 100 MB-class full grid editing is not guaranteed.
• Lines longer than about 8,000 characters render without token coloring to preserve responsiveness.
• Table View container cells are read-only summaries.
• BSON, split view, and multiple tabs are later-phase candidates.

License

Source code is licensed under the Mozilla Public License Version 2.0 (MPL-2.0); see LICENSE. Corresponding Source Code Form for executable packages is available from the matching GitHub tag, for example v1.3.0. The Visual JSON name, logo, screenshots, demo GIFs, image assets, and project branding are reserved and are not licensed under the MPL-2.0; see NOTICE.md. AvalonEdit remains licensed separately under MIT; see THIRD_PARTY_NOTICES.md. External contributions use DCO sign-off; see CONTRIBUTING.md.