AI-era dev utilities. Static, no signup.

UTF-8 safe encode and decode that round-trips emoji, CJK, and URL-safe variants.

Count tokens for GPT-4o, GPT-4, GPT-3.5 and more — tokenizer-exact, runs in your browser.

Side-by-side token counts for the same input across GPT-4o, GPT-4 Turbo, GPT-3.5, Claude, Gemini.

Pick a model, paste your prompt, see how much context you have left after reserving output tokens.

Estimate chunk count and embedding token spend from chunk size + overlap + corpus size.

Reference table of embedding model output dimensions, max input tokens, and pricing.

List-price reference for chat-model APIs across major providers, sortable and reviewed monthly.

Which frontier models support multimodal, vision, audio, JSON mode, and tool calling.

Pick a model, paste your prompt, set expected output length, see the per-call cost.

Plug in daily request volume + average token sizes, see monthly spend per model side-by-side.

Sanity-check whether your traffic stays within RPM and TPM ceilings for a given model and tier.

OpenAI ↔ Anthropic ↔ Gemini message format conversion. Paste one shape, get the other two.

Parse raw SSE bytes from any LLM streaming endpoint into events with reconstructed text.

Compose a Claude prompt as ordered XML-tagged sections — instructions, context, examples.

Wrap a JSON Schema as an OpenAI tool definition with optional strict mode.

Wrap a JSON Schema as an Anthropic tool definition for the messages API.

Extract tool definitions from an OpenAPI 3.x spec for OpenAI or Anthropic.

Compose a prompt with named variables, see the rendered output side-by-side.

Side-by-side line-level diff for two prompt variants — see exactly what changed.

Static analysis catching common prompt anti-patterns and surfacing token counts.

Drop input/output pairs, get them rendered as XML, Q&A, JSON, or markdown few-shot blocks.

Build the JSON entry for Claude Desktop or project-local .mcp.json — server name, command, args, env.

Validate an MCP tool definition against required fields, name format, schema shape, and conventions.

Pretty-print, minify, or validate JSON. Strict spec — catches trailing commas, unquoted keys, comments at the source.

Convert between JSON and YAML losslessly, preserving scalar types and structure.

Convert between flat JSON arrays and CSV / TSV — RFC 4180 quoting via PapaParse.

Test JSONPath queries against a sample document — recursive descent, filters, wildcards.

JavaScript-flavour regex tester with live highlighting, capture groups, and flag toggles.

URL encode / decode with three variants: encodeURIComponent, encodeURI, and form-urlencoded.

Generate UUID v4 (random) or v7 (time-ordered). Bulk regenerate up to 100 at once.

Convert between unix timestamps (seconds or ms) and human dates (ISO, RFC, local).

Decode JWT header and payload, see expiration status. No signature verification.