usefulweb.site: 111 focused tools that just work
Dependable little tools for people and AI agents. Calculators, checkers, planners and technical explorers with transparent assumptions. Every tool gives people a clear page and gives AI agents the identical result as JSON, OpenAPI and MCP.
Topics & themes
Everyday life & money
- Everyday problem-solving9 tools
- Money-saving & comparison9 tools
- Home, travel & daily life8 tools
- Internet, AI & productivity8 tools
- Contracts, safety & accessibility6 tools
Developer & data
Technical explorers
Everyday life & money
Everyday problem-solving
Decide, plan and sort out life admin with transparent calculations. · 9 tools
Cancellation Navigator
Verified steps to cancel Netflix, Spotify, Prime & more, plus a cancellation letter.
Deadline Decoder
Find every deadline, required action and consequence in a letter or notice.
Decision Simulator
Compare 2–6 choices by expected value, worst case, best case and minimax regret.
Form Translator
Plain-language help for confusing forms: field-by-field hints and jargon explained.
How Long Will It Last?
Estimate remaining life of appliances and home components and plan the replacement.
Is It Worth It?
Buy, rent, repair or subscribe? Compare total cost and NPV over the years you need it.
Life Admin Generator
A dated to-do list for moving, marriage, a baby, a new job and other life events.
Repair or Replace
Fix it or buy new? The 50% rule plus a cost-per-year check, with a clear verdict.
True Cost Calculator
What a car, pet, appliance, home or gadget really costs per year, month and day.
Money-saving & comparison
Compare prices, bills, salaries and subscriptions in real numbers. · 9 tools
Bill Detective
Spot spikes, price changes and calculation errors across your utility bills.
Break-even Explorer
When does an investment pay for itself? Payback, NPV and IRR for solar, EVs, heat pumps…
Bulk Buy Brain
Is the bulk pack really cheaper once waste, storage and tied-up cash are counted?
Hidden Fee Finder
Paste a quote, contract or invoice and see every fee, tax, penalty and add-on.
Inflation Time Machine
What was money from one year worth in another? CPI-based, 20 countries, World Bank data.
Price Per Everything
Compare products by price per gram, use, serving, hour or year of life.
Salary Reality Check
Compare job offers by real net pay per hour, including commute time and living costs.
Subscription Stack
Add up every subscription, spot overlaps and see which ones to cancel and what you save.
Warranty Value Calculator
Is the extended warranty worth it? Expected payout vs. price and break-even failure rate.
Home, travel & daily life
Furniture, moving, travel connections, food and home maintenance. · 8 tools
Food Storage Guide
How long is food safe in the fridge or freezer? Dates from the official FoodSafety.gov chart.
Household Maintenance Calendar
A dated home maintenance schedule for your appliances and features, as a calendar file.
Jet Lag Planner
A day-by-day sleep, light and caffeine plan to beat jet lag, with calendar export.
Leftover Chef
Turn leftovers and fridge odds and ends into 5 recipe ideas, using what expires first.
Moving Box Planner
How many moving boxes, how much tape, which truck and when to start packing.
Room Layout Optimizer
Auto-arrange furniture in a room around doors, windows and a clear walkway.
Travel Connection Checker
Estimate your odds of making a flight connection, step by step.
Will It Fit?
Check if a sofa, wardrobe or box fits through doors, corners, stairs and lifts.
Internet, AI & productivity
Understand errors, policies, scams, screenshots and AI answers. · 8 tools
AI Answer Verifier
Split an AI answer into claims and see which ones your sources actually support.
Error Message Translator
Paste a technical error and get the plain-English cause and troubleshooting steps.
File Format Doctor
Find out what a file really is from its bytes, why it will not open and how to convert it.
Privacy Policy Decoder
What a privacy policy says it collects, shares, sells and keeps — with quoted evidence.
Prompt-to-Tool Router
Describe your problem in plain words and get the right tools and order to use them.
Scam Signal Checker
Check a message or link for common scam and phishing warning signs — without clicking.
Screenshot to Steps
Turn a screenshot of an app or website into numbered steps for what you want to do.
Website Change Explainer
Compare two versions of a page and see which changes matter: prices, terms, dates, links.
Contracts, safety & accessibility
Contracts, laws, compatibility, accessibility and preparedness. · 6 tools
Accessibility Fixer
Turn WCAG 2.2 problems in your HTML into concrete code fixes, grouped by effort.
Before You Sign
Spot risky contract clauses (renewal, notice, liability, non-compete…) before you sign.
Digital Estate Organizer
List your online accounts and get a prioritised plan for what happens to them – no passwords needed.
Disaster Prep Builder
Build an emergency supply list for your household from official Ready.gov or BBK guidance.
The Compatibility Engine
Will this charger, cable, version or PC part work together? Rule-based checks with margins.
What Changed in This Law?
Compare two versions of a law or regulation section by section, with changed numbers and deadlines.
Developer & data
Developer & data tools
Deterministic helpers for developers, data and research. · 9 tools
HeaderLens
Is a website down? Multi-region status, redirects, TLS and security headers.
Accessibility Snapshot
Static WCAG 2.2 snapshot of a page: findings by severity, evidence and manual checks.
CiteShape
Paste a DOI, ORCID iD, ISBN or arXiv ID: validated, resolved, and formatted as APA, BibTeX and RIS.
DataFresh
Is this dataset or API still fresh? Newest record, update cadence check and schema drift.
FileFit
Can this app open, edit or convert that file format? Verified facts with sources.
LocaleKit Country Format Rules
Address form fields, postal-code regex, calling code and date formats for any country.
RuleDate Deadline Calculator
Business-day and deadline maths with public holidays and a step-by-step rule trace.
TimeFair Meeting Planner
Find fair meeting times across time zones, with DST-exact local times and rotation.
UnitProof Unit Calculator
Unit maths you can audit: dimension check, exact factors and a full derivation tree.
Technical explorers
Blockchain & Web3 explorers
Transactions, contracts, bridges, permissions, MEV and governance, decoded from the chain. · 15 tools
Account Abstraction Explorer
Decode ERC-4337 bundles: UserOperations, paymasters, gas per op, deployed smart accounts.
Blockchain Incident Replay
Replay an exploit from tx hashes: ordered timeline, fund-flow graph and who profited.
Bridge Transfer Tracker
Where is my bridged money? Finds the bridge deposit in a transaction and checks if it arrived.
Cross-Chain Transaction Explorer
Follow one transaction across chains: source tx, bridge deposit and destination fill on a timeline.
DAO Governance Explorer
Snapshot proposals, vote concentration, Governor state and treasury balances in one view.
DeFi Liquidation Explorer
Recent Aave V3 liquidations in USD, who liquidated whom, and a live health-factor check.
Gas Fee Intelligence Explorer
Live gas on 7 EVM chains: base fee, tips, trend and the USD cost of transfers and swaps.
MEV Explorer
Who extracted value in this block? Sandwiches, arbitrage, liquidations, builder and tips.
Rollup Batch Explorer
How L2 transactions reach Ethereum: unsafe → safe → finalized, blobs, batch costs, withdrawal waits.
Smart Contract Relationship Graph
Map a contract's proxy, implementation, admin, owner, deployer/factory and token links as a graph.
Smart Contract Upgrade Explorer
Is this smart contract upgradeable, who controls upgrades, and what changed?
Stablecoin Flow Explorer
USDC/USDT supply per chain, recent mints, burns and whale transfers, cross-chain totals.
Token Unlock Explorer
Model token vesting (cliff, linear, monthly, tranches, TGE) or audit a VestingWallet.
Transaction Decoder
See what an EVM transaction actually did: call, events, token transfers, fee, finality.
Wallet Permission Explorer
Who can move your tokens? Allowances, Permit2, NFT operators and EIP-7702 delegation, with risk.
Internet infrastructure explorers
DNS, BGP, certificates, IPv6, CDNs, e-mail and outages: the plumbing of the internet. · 11 tools
ASN Relationship Explorer
An autonomous system at a glance: holder, country, BGP neighbours and announced prefixes.
BGP Route Explorer
Who announces an IP or prefix in BGP: origin ASes, RPKI validity, visibility and origin changes.
CDN Behaviour Explorer
Which CDN serves a URL, whether it caches it (HIT/MISS, Age, TTL) and how, from two requests.
Certificate Transparency Explorer
Every logged certificate for a domain: history, issuers, subdomains, wildcards and expiry.
DNS + Certificate Explorer
DNS records, e-mail security, CAA, live TLS certificate and CT history for a domain.
Domain History Graph
Registration, DNS, hosting networks, certificates and Wayback captures of a domain as a timeline.
E-mail Infrastructure Explorer
MX, SPF lookups, DMARC, DKIM, MTA-STS, TLS-RPT and BIMI for a domain, scored with fixes.
Global DNS Explorer
Ask every authoritative name server and public resolvers: records, propagation, DNSSEC, mistakes.
HTTP Technology Explorer
Headers, compression, caching, HTTP/2-3 hints, redirects, security and tech stack for a URL.
Internet Outage Atlas
Correlate public outage signals (IODA, RIPEstat BGP, live probe) for a country, ASN or domain.
IPv6 Readiness Explorer
Is a domain reachable over IPv6? Web, DNS and mail checks, address classes and a scored report.
Security & supply-chain explorers
Vulnerabilities, SBOMs, containers, provenance, OAuth scopes and advisories. · 10 tools
Artifact Provenance Explorer
Verify npm build provenance: Sigstore signature, transparency log, source repo and commit.
Container Image Explorer
Inspect a container image: platforms, layers, base image, root user, labels and cosign signature.
CVE Relationship Graph
One CVE or GHSA as a graph: aliases, affected packages, fixed versions, KEV status and EPSS.
Dependency Vulnerability Explorer
Known vulnerabilities in your dependencies, and the version that fixes each one.
OAuth Permission Explorer
What an OAuth consent request really allows: scopes, risky combinations and flow problems.
Open Source Trust Explorer
Is this open-source project maintained and trustworthy? Scorecard, activity and provenance.
Package Ecosystem Graph
Who depends on what: resolved dependency graph, duplicates and the blast radius of breaking changes.
SBOM Explorer
Open a CycloneDX or SPDX SBOM: components, licences, dependency tree and known vulnerabilities.
Security Advisory Timeline
Disclosures, affected ranges, fixes and withdrawals for a package on one timeline, with time-to-fix.
Security Configuration Scanner
Passive, graded check of a domain's TLS, security headers, DNS security and security.txt.
Developer & cloud explorers
APIs, Kubernetes, traces, query plans, Terraform, CI, serverless, lineage and cron. · 10 tools
API Explorer of Explorers
Search 2,500+ public APIs or summarise any OpenAPI spec: servers, auth, endpoints, changes.
CI/CD Failure Explorer
Paste CI logs from several runs: root cause per run, grouped signatures, top causes and fixes.
Cron Job Explorer
Paste a crontab or CronJob YAML: plain-English schedules, DST-exact next runs, herds and overlaps.
Data Lineage Explorer
Paste SQL or dbt models: table lineage graph, column lineage and upstream/downstream of any field.
Distributed Trace Explorer
Paste an OTLP, Jaeger or Zipkin trace: span tree, critical path, self-time, N+1 calls and errors.
Kubernetes Event Explorer
Paste kubectl events and get a timeline, reason taxonomy and likely root causes per workload.
OpenAPI Diff Explorer
Compare two versions of an OpenAPI spec and see exactly which changes break clients.
Query Plan Visualizer
PostgreSQL EXPLAIN (ANALYZE) or MySQL EXPLAIN JSON → plan tree, hot nodes and index suggestions.
Serverless Performance Explorer
Lambda REPORT lines → cold-start rate, p50/p95/p99, memory right-sizing and cost per 1M calls.
Terraform Plan & Drift Explorer
Paste terraform show -json: drift, replacement reasons, attribute diffs and risky deletes.
AI infrastructure & agent explorers
MCP servers, agent tools, traces, models, costs, RAG citations and structured output. · 10 tools
Agent Permission Graph
See what your AI agent can reach: MCP servers, commands, files, network and secrets – with risks.
AI Agent Tool Explorer
Index of tools AI agents can call: this site, the MCP Registry or your definitions, by capability.
AI Model Compatibility Explorer
Which LLMs take images, audio or files, fit your context and support tools or structured outputs?
AI Tool-Call Trace Explorer
Paste an agent transcript: see every tool call in order, with errors, timings, retries and loops.
AI Website Readiness Explorer
Can ChatGPT, Claude, Perplexity and AI agents read your website? Explainable score.
LLM Cost Explorer
Monthly LLM API cost per model for your workload, with prompt-caching and batch savings.
MCP Server Explorer
Inspect any MCP server before you connect an AI agent: tools, permissions, risks, changes over time.
Model Behavior Regression Explorer
Compare eval results of two model versions: accuracy, regressions, McNemar p-value, flaky items.
RAG Citation Debugger
Check a RAG answer's citations against the retrieved chunks: uncited claims, wrong sources, numbers.
Structured Output Validator
Validate AI JSON output against a JSON Schema: parse errors with line/column, plain-language fixes.
Public technical data explorers
Public spending, energy grids, satellite imagery, software adoption and web history. · 5 tools
Energy Grid Explorer
Generation mix, load, renewable share, cross-border flows and power prices for European grids.
Internet Archive Change Explorer
See how a web page changed in the Wayback Machine: capture timeline plus the changes that matter.
Public Spending Explorer
Search government contracts and grants: who pays whom, totals per agency and vendor.
Satellite Change Explorer
Compare NASA satellite images of any place on two dates: true colour, NDVI, night lights.
Software Adoption Explorer
Open-source usage signals: weekly downloads, growth and version adoption for npm, PyPI, crates.
Explorer of Everything
One search box across every explorer. · 1 tools
Explorer of Everything
Search transactions, contracts, domains, packages, advisories, MCP servers and websites in one box.
Workflows: tools that work together
Moving home
Personalised moving checklist with deadlines, box and van estimate, an optional "will the sofa fit?" check, and a maintenance calendar for the new place.
Is this message a scam?
Analyses a suspicious e-mail/SMS for scam signals, then checks the reachability and security headers of the linked website. Never claims a message is safe.
Subscription clean-up
Totals your subscriptions, flags overlaps and poor value, and gives verified cancellation steps for the one you want to cancel first.