Methodology & Data Sources
Last updated: September 4, 2026
Why you can trust the numbers here
Every calculator on FreeToolHub follows the same three commitments: transparent logic (you can see what's being calculated), traceable data (every dataset links to its authoritative source), and client-first privacy (calculations run in your browser, not on a server). There are no hidden margins, no black-box assumptions, and no data funneled back to us.
We maintain a central data registry that records — for each dataset — its source, update frequency, last-verified date, and how it is auto-maintained. Today that registry tracks 54 datasets across the site, of which 2 are fetched live from public APIs. See the corrections log for our record of finding and fixing data errors.
Editorial & review policy
FreeToolHub is built and maintained by KingCavan (Founder & Lead Developer — more on the About page). There is no content team, no AI-generated filler, and no outsourced “SEO articles.” Every guide is written against the same code that powers the matching calculator, then reviewed by hand before it ships.
- Creation — guides start from the questions the underlying tool actually answers (formulas, thresholds, worked examples), not from keyword-first outlines.
- Review — every worked example is checked against the tool's live output before publication; the formula shown on the page and the formula in the code must agree.
- Updates — when a tax year, threshold, or platform fee changes, the affected datasets are re-verified (see the freshness checks below) and the guide text is updated to match.
- “Last updated” dates — the date shown on each guide and in its structured data comes from our real revision history (git) for that article. We do not publish invented dates.
- Corrections — found an error? The corrections log is the public record of what changed and why. Reports go through the contact page.
- Independence — no affiliate links inside calculators; rankings and recommendations are not for sale.
How our data updates
We classify and update datasets by how volatile they are. This table describes the five update tiers we use, with real examples currently live on the site.
| Frequency | Meaning | Example datasets |
|---|---|---|
| realtime1 set(s) | Fetched live on page load from a public API. The most volatile data, e.g. currency exchange rates. | Guerrilla Mail Temporary Email API |
| daily1 set(s) | Refreshed once per business day, typically from a daily-published feed. | Currency Exchange Rates |
| monthly4 set(s) | Updated monthly from scheduled publications, e.g. the monthly CPI release. | Inflation Rate (CPI-U) Time Zone Database (IANA) Social Media Image Dimensions 2026 |
| annual22 set(s) | Refreshed yearly, aligned to an official annual publication such as IRS tax-year inflation adjustments. | Federal Income Tax Brackets Social Security Wage Base HSA / FSA Contribution Limits |
| manual26 set(s) | Verified manually only when the underlying rate or rule changes, e.g. platform fees or NIIT thresholds. | Net Investment Income Tax Thresholds LLC Formation & Annual Fees by State Payment Processor Fee Rates |
Where the data comes from
We prefer primary, authoritative sources and link every dataset back to them. On each tool page the relevant sources are shown alongside a per-dataset disclaimer. Representative sources include:
- IRS — tax brackets, deductions, retirement limits, withholding (IRS.gov)
- SSA — Social Security wage base (ssa.gov/OACT)
- BLS — Consumer Price Index for inflation (bls.gov/cpi)
- U.S. Dept. of State — monthly Visa Bulletin
- Freddie Mac PMMS — mortgage rate benchmark
- ECB reference rates via Frankfurter API — currency
- EU Council & national agencies — VAT rates
- State Departments of Revenue / Secretary of State — sales tax, income tax, LLC fees
- MDN / W3C — browser-native APIs & format specifications
- Vendor pricing pages — payment processors, LLM APIs, hosting platforms
For privacy and data-handling details, see our Privacy Policy. For the full list of our tools and categories, browse the tool directory.
How we verify the data
Data integrity is checked two ways, and both are automated where possible.
The data-maintenance pipeline is fully client-side — it performs checks and generates reports without uploading any site data. For the technical details, see the data-maintenance module in our project notes.
Our privacy commitment
The overwhelming majority of FreeToolHub calculations run entirely in your browser. Your files, income, and personal values are processed locally and are never sent to our servers. The only exceptions are AI-powered tools that use an external model API, and those are clearly labeled and only happen when you explicitly submit your content.
We use privacy-friendly, cookieless analytics (Plausible) for anonymous page statistics. Read the full details in our Privacy Policy.
Update & correction history
This log records notable dataset updates and data corrections. Every entry references the primary source that drove the change. Errors we find are corrected transparently here.