Tools that make
the hard parts tangible.
Interactive visualizers, estimators and playgrounds for builders — the kind of thing you wish existed when you were stuck on a system-design diagram or a RAG pipeline. Every tool is free, needs no account, and runs entirely on your device.
Consistent Hashing Visualizer
Watch keys rebalance on the hash ring as nodes come and go.
Interactive Capacity Estimator
Back-of-the-envelope math for system design, with the reasoning shown.
RAG Chunking Playground
Paste a document, pick a strategy, see the actual chunks and tokens.
Context Budget & Cost Planner
Model an agent’s context window and see where the tokens (and dollars) go.
Quorum (N/R/W) Explorer
Set N, R and W and instantly see your consistency–availability trade-off.
Availability (Nines) Calculator
Compose services in series and parallel to find your real uptime.
LLM-as-Judge Rubric Builder
Design an eval rubric and generate the judge prompt for it.
Tool-Schema Designer
Build a function-calling tool definition visually, get valid JSON out.
Percentile Calculator
Paste your numbers and see p50, p90, p95 and p99 — the tail, not the average.
LLM Pricing Comparator
Enter your token usage and see the monthly bill across every major model.
Bloom Filter Sizing
Pick your item count and false-positive rate — get bits, memory and hash count.
Token Bucket Simulator
Fire requests at a rate limiter and watch tokens drain, refill and throttle.
Context Window Visualizer
See your prompt fill the context window — and where it overflows.
Token Counter
Paste text, get tokens — plus what it costs and how much window it eats.
GPU VRAM Calculator
Will that model fit on your GPU? Weights + KV cache + overhead, computed.
Fine-Tuning Cost Estimator
What will that fine-tune actually cost? GPUs, hours, dollars — before you rent anything.
KV Cache Calculator
The memory that actually caps your concurrency — per token, per sequence, per batch.
Embedding Cost Calculator
Price your RAG index before you build it: embedding spend, vector storage, query costs.
Latency Budget Builder
Where does the second go? Build the request waterfall and find the TTFT bottleneck.
SLO Burn-Rate Calculator
How fast are you spending the error budget — and when does the pager fire?
Model Comparison Table
Every model that matters, one sortable table — priced at YOUR input:output ratio.
Training Compute Calculator
How much compute, time and money to train a model of N params on D tokens.
Little's Law Calculator
Concurrency = throughput × latency. Give any two, get the third.
Prompt Caching Savings Calculator
Model prompt-cache hit rate, the write premium, and your real $/request.
JWT Decoder
Paste a JSON Web Token, read its header, claims and expiry — offline.
CIDR Calculator
Type an IPv4 CIDR block, get the network, broadcast, range and host count.
Unix Time Converter
Epoch ↔ human date, in seconds or milliseconds, UTC and local.
UUID & ULID Generator
Generate v4 UUIDs and ULIDs in bulk — cryptographically random, in-browser.
Regex Tester
Write a pattern, paste text, see every match and capture group live.
Base64 & URL Encoder
Encode or decode Base64, Base64URL and percent-encoding — UTF-8 safe.
Chmod Calculator
Click permissions to get the octal, or type octal to see the rwx.
Password Entropy Calculator
See a password’s entropy in bits and how long it would take to crack.
Cron Expression Builder
Write a cron expression, read it in plain English, see the next run times.
SQL Formatter
Paste a one-line query, get readable, indented SQL.
Markdown Table Generator
Paste CSV or TSV, get a clean, aligned Markdown table.
Diff Checker
Compare two blocks of text and see exactly what changed, line by line.
A/B Test Significance Calculator
Enter two variants’ conversions and see if the difference is real.
Kafka Partition Calculator
Size a topic’s partitions from your throughput and consumer targets.
Connection Pool Sizer
Size a DB connection pool from QPS and latency — and check the DB’s limit.
Database Index Size Estimator
Estimate how much disk a B-tree index will take before you create it.
JSON Formatter & Diff
Validate and pretty-print JSON — or diff two JSON documents by value.
Cache ROI Calculator
See what a cache buys you: latency saved and backend load removed.
Storage Growth Forecaster
Project how big your data gets — and when you’ll run out of disk.
Rate Limit Designer
Turn a target rate and burst into concrete token-bucket parameters.
Agent Loop Cost Estimator
See why an agent’s cost grows faster than its number of steps.
Sharding Planner
How many shards you need from data size, QPS and per-shard limits.
Embedding Dimension Tradeoff
See what vector dimensions cost in memory before you pick them.
Latency Numbers Explorer
The latency numbers every engineer should know — scaled to human time.
GPU Rental Price Reference
Compare cloud GPU hourly rates and estimate a job’s compute cost.
NPU Model-Fit Calculator
Given an NPU’s TOPS and RAM, see which local models fit and how fast they prefill.
Agent Time-Horizon Explorer
Project the METR doubling curve: when do agents reliably handle day- and week-long tasks?
Skill Linter
Paste a SKILL.md and score it against a Claude-Skills quality rubric — before an agent has to use it.
EU AI Act Timeline
What applies on 2 Aug 2026 vs later — mapped to the engineering artifacts you actually have to ship.
AI Salary Explorer
Indicative 2026 AI-engineering comp bands by role, level and company tier.
Exponential Backoff Calculator
Turn base delay, multiplier and cap into a real retry schedule — with jitter.
Cosine Similarity Calculator
Enter two vectors and see cosine similarity, distance and the angle between them.
LLM Sampling Simulator
See how temperature, top-p and top-k reshape the next-token probabilities.
FDE Comp Explorer
Six employer tiers, five levels, four markets — and the equity share nobody shows you.
Scoping Question Log
You get six questions. Which six turn “we want AI for X” into something you can build?
Tools — frequently asked questions
Are these developer tools free?
Yes. Every tool on Vibe Engines is completely free, with no account, sign-up, or payment required. They run entirely in your browser — nothing you type is sent to a server.
Do I need to install anything or create an account?
No. Each tool is a self-contained web page that loads instantly and runs client-side in your browser. There is nothing to install and no login.
Is my data private when I use these tools?
Yes. The tools compute everything locally in your browser. Text, numbers, and documents you enter never leave your device, so you can safely use them with work-related inputs.
Who are these tools for?
They are built for software engineers, backend and AI builders, and anyone preparing for system-design or AI-engineering interviews — interactive visualizers and estimators that make hard concepts tangible.
Can I suggest a tool?
Absolutely. The coming-soon list is shaped by what builders ask for. Use the "Suggest a tool" link on this page to send an idea, and the best ones get built next.
Got a tool you wish existed?
These are built for builders. If there’s an interactive tool that would make your work easier, tell me — the best ideas become the next ones I ship.
Suggest a tool →