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Subnets Preview
Open your subnet layout JSON in the Visual Subnet Calculator inside Simple Browser — next to your code, with a short shareable ?c=v1… link (same format as Copy Link on the web app).
Quick start
Open a workspace that contains a v0-subnets JSON export (optional).
Command Palette → Subnet: Preview JSON (Cmd+Shift+P / Ctrl+Shift+P).
Simple Browser opens https://v0-subnets.vercel.app/?c=v1… with your layout loaded.
Tip: bind a shortcut to network.subnetPreview.open.
What it does
Opens the calculator in Simple Browser (no external browser required).
Uses the focused .json when it is a valid v0-subnets export; otherwise finds configs by glob.
Builds a compressed preview URL in-process (deflate-raw → ?c=v1…).
Falls back to an empty calculator when no config is present (configurable).
No telemetry from the extension. Reads workspace JSON locally only.
Which file is opened?
Situation
Result
Focused editor has valid v0-subnets JSON
That file
No valid JSON focused
Latest match of network.subnetPreview.configGlob (default docs/subnet-config-*.json)
Primary glob finds nothing
network.subnetPreview.configFallbackGlobs (default **/*subnet-config*.json)
Multiple matches
Latest path (sorted); set promptWhenMultiple to pick
No config in workspace
Empty calculator if openEmptyWhenMissing is on
Re-run the command after you save JSON changes — an already-open Simple Browser tab does not auto-refresh.
Example JSON
Compatible with exports from v0-subnets.vercel.app :
{
"networkAddress": "10.0.0.0",
"maskBits": "16",
"subnets": [
{
"networkAddress": "10.0.0.0",
"maskBits": 24,
"prefix": "app-uat",
"color": "blue"
}
]
}
Minimum shape: networkAddress + subnets[] (each subnet needs networkAddress).
Settings
Setting
Default
Description
network.subnetPreview.configGlobdocs/subnet-config-*.jsonPrimary workspace glob
network.subnetPreview.configFallbackGlobs["**/*subnet-config*.json"]Extra globs if primary finds nothing
network.subnetPreview.promptWhenMultiplefalseShow a picker when multiple configs match
network.subnetPreview.openEmptyWhenMissingtrueOpen empty calculator when nothing matches
Privacy & security
Topic
Behavior
Telemetry
None from this extension
Workspace files
Read locally via the VS Code API only
Preview host
Fixed to https://v0-subnets.vercel.app/
URL contents
Layout data (CIDRs, names/notes, colors) is sent in the query string to load the page — avoid secrets or personal data in notes
Path safety
Config must stay inside the workspace; JSON validated and capped at 1 MiB
Errors
Generic toasts (no filesystem paths)
Requirements
VS Code 1.80+ or Cursor with Simple Browser
A workspace folder open (not a single loose file)
Links
License
MIT
