Tools that load instantly.
No popups, no signup walls, no laggy SPAs. Each tool is a tiny static page on its own subdomain — bookmark the one you use. 62 tools, 100% client-side — your data stays in your browser. Browse all →
Developer tools
Encode, decode, validate, generate. Built for the address bar.
- GUID / UUID Generate and decode UUIDs (v1, v3, v4, v5, v7, nil) — bulk, validate, language guides. guid.tooljo.com
- JSON Format, minify, validate JSON; convert to YAML — instant, browser-only. json.tooljo.com
- Markdown Live markdown viewer with URL-hash sharing, MD↔HTML round-trip, and a complete cheat sheet. md.tooljo.com
- Base64 Encode/decode UTF-8 text, URL-safe variant, file → data URI. base64.tooljo.com
- Regex Live regex tester with capture groups, find-and-replace, and a complete syntax cheat sheet. regex.tooljo.com
- JWT Decode, verify HMAC, and sign JWTs (HS256/384/512) — entirely in your browser. jwt.tooljo.com
- Hash MD5, SHA-1, SHA-256, SHA-384, SHA-512 — text or file. Compare two hashes to verify downloads. hash.tooljo.com
- Password Crypto-secure password / passphrase generator with real entropy meter and strength checker. password.tooljo.com
- QR QR code generator — text, URLs, Wi-Fi, vCard. SVG + PNG download. Self-contained encoder, no upload. qr.tooljo.com
- Cron Cron expression parser — explain crontab in plain English, validate, and see the next 5 fire times in your local timezone. cron.tooljo.com
- Diff Text diff viewer — side-by-side + unified, line + word highlighting, ignore-whitespace + ignore-case. diff.tooljo.com
- Dev tools Fast, free, browser-only developer tools — hub linking UUID, JSON, base64, regex, JWT, hash, password, QR, cron, diff. dev.tooljo.com
Utilities
Date, time, color — the things you Google five times a week.
- Epoch Unix timestamp converter — auto-detects sec/ms/µs/ns/ISO/RFC. Live now-clock. epoch.tooljo.com
- Color Hex / RGB / HSL / OKLCH converter, eyedropper, presets, recents, WCAG contrast checker. hex.tooljo.com
- Date Days between two dates, add/subtract days, live countdown to any future date. date.tooljo.com
- Converters Conversion tools hub — units, timezones, currency, color, dates, encodings. convert.tooljo.com
- Unit converter Universal unit converter — length, weight, temperature, volume, area, speed. All conversions in your browser, no upload, instant. unit.tooljo.com
- Timezone converter Convert between timezones with DST awareness. Visual day-night strip. All major IANA timezones supported. timezone.tooljo.com
- Currency converter Currency converter with daily-updated rates. 30+ currencies. Static rate file means privacy is preserved — no external API at runtime. currency.tooljo.com
- Percentage calculator Percentage calculator — what is X% of Y, X is what percent of Y, and percent increase or decrease between two numbers. Browser-only, no signup. percent.tooljo.com
Finance
Plain-English calculators with shareable scenarios. No email gate.
- Mortgage Mortgage payment calculator with PITI + extra-principal payoff. Shareable scenario URLs. finance.tooljo.com
- Personal finance Personal finance hub — mortgage, debt, loan, compound interest, FIRE, retirement, savings, refinance, ROI, and more. Plain-English math, browser-only. money.tooljo.com
- Debt payoff Free debt payoff calculator — snowball + avalanche methods. See your debt-free date, total interest, and the optimal order to pay debts off. debt.tooljo.com
- Compound interest Compound interest calculator — see how monthly contributions plus time grow your money. Daily/monthly/annual compounding, year-by-year table, shareable URLs. Browser-only, no signup. compound.tooljo.com
- FIRE calculator FIRE calculator — financial independence / retire early. Your FIRE number from the 4% rule, years to FI, progress, and a real-return projection. Browser-only, no signup. fire.tooljo.com
- Savings goal Savings goal calculator — set a target and date to get the monthly amount you need, or set a monthly amount to see when you'll hit the goal. Browser-only, no signup. savings.tooljo.com
- Loan calculator Loan calculator — monthly payment, total interest, and full amortization schedule for car, personal, and student loans. Shareable URLs, browser-only. loan.tooljo.com
- Salary to hourly Salary to hourly calculator — convert an annual salary to hourly, daily, weekly, biweekly, and monthly pay, and back again. Adjust hours per week and weeks per year. Browser-only, no signup. salary.tooljo.com
- ROI calculator ROI calculator — return on investment percentage, total gain or loss, and annualized return (CAGR) from a starting value, ending value, and holding period. Browser-only, no signup. roi.tooljo.com
- Refinance calculator Mortgage refinance calculator — compare your current loan to a new rate and term. Monthly savings, break-even month on closing costs, and lifetime interest difference. Browser-only, no signup. refinance.tooljo.com
- Inflation calculator Inflation calculator — see how inflation erodes buying power over time. What a sum will cost in the future and what it will be worth in today's dollars, at any assumed rate. Browser-only, no signup. inflation.tooljo.com
- APY calculator APY calculator — convert APR to APY (effective annual yield) and see how compounding frequency changes your real return. Compare annual, monthly, daily, and continuous. Browser-only, no signup. apy.tooljo.com
- Sales tax calculator Sales tax calculator — add sales tax to a price or pull it out of a tax-inclusive total. Any rate, instant, browser-only, no signup. salestax.tooljo.com
- Tip calculator Tip calculator — tip amount, total, and per-person split for any bill. Quick 15/18/20/25% presets, custom rate. Browser-only, no signup. tip.tooljo.com
- Discount calculator Discount calculator — final price after a percent-off, the amount you save, and stacked discounts. Browser-only, no signup. discount.tooljo.com
- Home affordability Home affordability calculator — how much house you can afford from income, debts, down payment, and rate, using the 28/36 DTI rule. Browser-only, no signup. afford.tooljo.com
- Retirement calculator Retirement calculator — project your 401(k) balance with employer match, contribution rate, and expected return. See how much the match adds. Browser-only, no signup. retirement.tooljo.com
- Credit card payoff Credit card payoff calculator — months to clear a balance, total interest, and the minimum-payment trap. Browser-only, no signup. creditcard.tooljo.com
- CD calculator CD calculator — maturity value and interest earned on a certificate of deposit from your deposit, APY, and term. Browser-only, no signup. cd.tooljo.com
- Emergency fund Emergency fund calculator — how big your safety net should be (3–12 months of expenses), the gap to your target, and how long to get there. Browser-only, no signup. emergencyfund.tooljo.com
- Retirement drawdown Retirement drawdown calculator — how long your savings last at a given withdrawal and return, or whether withdrawals are sustainable. Browser-only, no signup. drawdown.tooljo.com
- Annuity calculator Annuity calculator — the monthly income a lump sum provides over a set term at a given return, plus total payout and interest earned. Browser-only, no signup. annuity.tooljo.com
- Dividend calculator Dividend calculator — annual, quarterly, and monthly income from a dividend yield, plus a reinvestment (DRIP) growth projection. Browser-only, no signup. dividend.tooljo.com
- Simple interest Simple interest calculator — interest and total from principal, rate, and time using I = P x r x t, with a side-by-side compound comparison. Browser-only, no signup. simpleinterest.tooljo.com
- Budget calculator Budget calculator — split your monthly take-home pay with the 50/30/20 rule (needs, wants, savings), or your own percentages. Browser-only, no signup. budget.tooljo.com
- Cap rate calculator Cap rate calculator — capitalization rate, NOI, monthly cash flow, and cash-on-cash return for a rental property. Browser-only, no signup. caprate.tooljo.com
- Startup runway Startup runway calculator — how many months of cash you have left from your burn rate, and your zero-cash date. Browser-only, no signup. runway.tooljo.com
Fitness + cardio
Pace, splits, race prediction, erg watts. Honest math.
- Running pace Running pace + splits + Riegel race-time predictor. Marathon, half, 10K, 5K presets. pace.tooljo.com
- Erg calculator Concept2 RowErg / SkiErg / BikeErg watts ↔ split ↔ time ↔ distance. pace.tooljo.com/erg
- Health Health hub — BMI live, plus BMR / TDEE / calorie / macro tools coming soon. Plain-English math, browser-only. health.tooljo.com
- BMI calculator Free BMI calculator — metric and imperial inputs, WHO + Asian-population thresholds. Browser-only, no signup, no health data uploaded. bmi.tooljo.com
- BMR calculator Free BMR calculator — basal metabolic rate via Mifflin-St Jeor (modern) and Harris-Benedict. Browser-only. bmr.tooljo.com
- TDEE calculator Free TDEE calculator — total daily energy expenditure with sensitivity ranges. Browser-only. tdee.tooljo.com
- Macro calculator Free macro calculator — TDEE → calorie target → protein/carb/fat split. Cut/maintain/bulk modes. macro.tooljo.com
From the blog network
Long-form posts on the practical problems each tool exists to solve.
- guid.tooljo.com Stripe / Discord / Shopify ID systems compared Why each of the big platforms invented its own ID format — and which one to copy for your own service.
- jwt.tooljo.com JWT claims your auth team forgets to check iss, aud, jti, nbf, sub. The JWT spec defines them for a reason — but most production code only checks exp.
- epoch.tooljo.com Five timestamp formats that cause production outages Off-by-1000-ms, the 2038 problem, the 1582 UUID epoch, ISO 8601 ambiguity, DST gaps.
- hash.tooljo.com Why MD5 still won't die MD5 is broken for security and has been since 2004. So why is it still everywhere?
- regex.tooljo.com Catastrophic backtracking — patterns that DoS Five regex shapes that turn O(n) into O(2^n). Each has taken down production at companies you've heard of.
- base64.tooljo.com Base64 isn't encryption Five places engineers still confuse encoding with encryption — and what each costs in production.
- hex.tooljo.com Why your design system needs OKLCH Same lightness, perceived. Tonal scales that actually look tonal. Dark themes by inverting L.
- date.tooljo.com Inclusive vs exclusive day counting Vacation accruals, free trials, prison sentences, lease terms. Where the off-by-one hides.
- pace.tooljo.com Two pacing myths I wish someone had killed earlier Even splits aren't optimal. Long-run pace shouldn't equal marathon pace minus 30 sec/km.
- finance.tooljo.com Why early extra principal saves 6× as much $200/month for years 1–10 vs years 21–30 of a 30-year mortgage. The math is dramatic.
Why the network exists
Most online dev / utility tools are 5 MB SPAs that take 3 seconds to show a text input, plus an email gate, plus an upsell. We're building the opposite: each tool is a static page under 30 KB with no signup, no upload, no laggy framework. Pages render instantly and run entirely in your browser.
Each subdomain is independently deployable; a single shared Caddy on the VPS routes by Host header. Press ⌘K (or /) on any page for the cross-network command palette — it auto-detects what you've pasted (UUID, JWT, JSON, color, timestamp, hash) and jumps to the right tool.
What's coming
Category hubs are live at dev.tooljo.com and
money.tooljo.com, with convert.tooljo.com
next. Tools on the roadmap: unit (universal
converter), timezone (DST-aware ranges), and
currency (daily static rates). The general rule:
each new tool goes live the day it ships rather than waiting
for a "launch."
Want one we don't have yet? Request a tool → — every email goes to the founder.