Unit Prefix Sanity Checker

About

Stop unit prefix errors before they reach production.
Unit Prefix Sanity Checker scans any web page — datasheets, spec documents, BOMs, wiki articles — and highlights engineering values that look wrong. It catches the mistakes that spell-checkers can't: a millivolt where you meant a volt, a millifarad where you meant a microfarad, a megabit where you meant a megabyte.
133 detection rules across 11 engineering domains: electrical, frequency, data, length, mass, pressure, temperature, mechanical, chemical, radiation, and optical.
HOW IT WORKS
The engine reads the surrounding text to understand context, not just the number. "10 mF ceramic capacitor" gets flagged (probably means 10 µF). "10 mF supercapacitor" does not (millifarads are correct for supercaps). Every finding has a confidence score so you can focus on what matters.
Hover over any highlight to see what's wrong, why it was flagged, and a suggested fix. Click to copy the suggestion. Click a finding in the popup panel to jump straight to it on the page.
WHAT IT CATCHES

Prefix magnitude errors: 10000 mV → should be 10 V
Bit/byte confusion: 500 Mb → probably meant 500 MB
Case sensitivity: mhz → should be MHz, ma → should be mA
Out-of-range values: 2500 °C operating temp, pH of 15
Tolerance errors: ±100% on a resistor
Missing units: R1=4700 (missing Ω)
Non-standard resistor values: 14 kΩ not in E24 series
Inverted ranges: "85 to -40 °C" (lower bound should come first)
Contradictory specs: same parameter listed as two different values
Mixed unit systems: mm and inches in the same document

CATEGORIES
Electrical · Frequency · Data (bits/bytes) · Length · Mass · Pressure · Temperature · Mechanical · Chemical · Radiation · Optical
Enable or disable any category from the popup. Working on an RF design? Turn on just Electrical and Frequency. Reviewing a BOM? Turn on everything.
PRIVACY
Runs 100% locally in your browser. No data leaves your machine. No accounts, no tracking, no analytics. The only network call the extension ever makes is license key validation for premium users, and only to the LemonSqueezy API (api.lemonsqueezy.com).
PREMIUM ($8/month)
Upgrade for power-user features:
→ Custom Rules Editor — Write your own detection rules with regex patterns, value ranges, context keywords, and suggestions. Import/export rules as JSON to share with your team.
→ BOM Upload Scanner — Drag and drop a CSV/TSV bill of materials. Scans every cell and shows issues by row and column with severity breakdown.
→ Cross-Value Analysis — Detects patterns across all values on the page: prefix consistency outliers, 1000× jumps between nearby values, non-standard E-series resistors, magnitude outliers, inverted ranges, contradictory specs, and mixed unit systems.
→ Enhanced Export — Export findings as CSV (structured columns) or styled HTML reports in addition to plain text.
→ Dismiss & Whitelist — Dismiss individual findings per-page or globally. Manage your dismissed list with one-click restore.
→ Findings History — Every scan is logged. See totals, weekly/monthly trends, and top-flagged domains on a built-in dashboard.
→ Domain Profiles — Pre-built configurations for Power Electronics, RF/Microwave, HVAC, Chemical/Process, Automotive, and Aerospace. Each profile tunes which categories are active, minimum confidence thresholds, and severity weights.
→ Page Change Monitor — Watch a page for value changes. The extension checks every 4 hours and alerts you when specs are added or removed.
The free version is fully functional — premium just adds workflow features for engineers who use this daily.