Data Sources
Every fact on this site traces to one of the source classes below. Safety-critical values come only from Tier 1 official documentation; retailer data is used for price and availability only; everything carries a retrieval date so you can judge freshness yourself.
Last updated: 2026-08-24.
Source classes and reliability tiers
| Tier | Sources | Used for | Restrictions |
|---|---|---|---|
| Tier 1 — Official documentation | Official product manuals; manufacturer specification pages; CPSC (recalls, regulations); NHTSA (car seats); FDA (where relevant, e.g., breast pumps); official government regulations; official recall notices; recognized standards bodies where publicly available | All safety-critical fields: weight/height limits, rear-facing limits, installation and tether rules, infant-insert requirements, expiration/lifespan rules, recall status, certification claims, regulatory claims | Sole acceptable basis for safety-critical claims. Two independent Tier 1 sources preferred where available. |
| Tier 2 — Authorized retail | Listings from authorized retailers and verified marketplace pricing (e.g., Amazon Creators API) | Price, availability, current offers, bundle contents as sold | Never used for specifications or safety claims — listing specs are frequently wrong or conflated across variants. |
| Tier 3 — Context only | Public standards summaries, reputable press coverage of product launches | Background context, launch timing, line-up orientation | Never the sole basis for any published factual claim; always superseded by Tier 1 when Tier 1 exists. |
Conflict rule: fail closed
If two Tier 1 sources conflict — say, a manual states one rear-facing limit while the manufacturer's product page states another — no definitive claim is published. The comparison shows the conflict itself, for example: "Current sources conflict on this limit. Verify the current product manual before use." A plausible-looking average is never published. This applies to every safety-critical field without exception. Fail-closed handling extends to availability: the YOYO2 review reports that no verified Amazon US listing exists instead of inventing a price.
Retrieval-date discipline
- Every sourced value is stamped with its retrieval date. Spec tables cite it in the caption ("retrieved 2026-08-23"); source lists show per-source access dates.
- Dates are shown to readers, not hidden in metadata, so freshness can be judged before trusting a number.
- Stale values are rechecked before republishing. If a stored record is older than its category's recheck interval, the source is re-fetched first; if re-fetching fails, affected fields fall back to UNKNOWN rather than silently persisting old numbers.
- Prices are re-verified at publish time and always paired with live retailer links, because prices drift fastest.
- Recall status is checked against CPSC/NHTSA immediately before publish and on every scheduled recheck thereafter (see recall monitoring; worked example: Extend2Fit review, whose spec table shows a stated source conflict rather than a picked number).
Sources deliberately excluded
- Anonymous blogs, forums, and social-media threads — unverifiable provenance.
- Retailer customer Q&A and reviews — useful signal for shoppers, not an acceptable basis for published specifications.
- AI-generated aggregator articles — circular sourcing with no accountable origin.
- Unlicensed reseller listings — frequently mislabeled variants or regional models.
- Anything requiring confidential access — only publicly available documentation is used.
See it applied: each comparison page ends with a numbered sources list including retrieval dates — e.g., Joolz Aer² vs Bugaboo Butterfly 2 or Extend2Fit vs ClickTight. Related: AI methodology · Editorial policy · Corrections
Conflicts are stated
When two primary sources disagree — a manual states one rear-facing limit while the manufacturer's product page states another — we do not publish a definitive figure. The comparison shows the conflict itself: both values, both sources, both retrieval dates, side by side, plus an instruction to verify the current manual before use. A conflict is information for the reader, not an embarrassment to be smoothed into false certainty. This is the same fail-closed rule our source tiers enforce: no majority vote between primaries, no silent pick of whichever number reads better.
No invented experts
There are no fake experts, fabricated testimonials, or invented quotes anywhere on this site. We have not used the product in a nursery and we will not pretend otherwise: no reviewer persona, no "our lab", no stock-photo parent vouching for a verdict. Every claim traces to a named primary source with a retrieval date; where no source exists, the page says so instead of manufacturing authority. What we publish is verified documentation, not simulated experience.
Safety language discipline
Safety claims get the most conservative wording we can defend. We cite the federal standard by name (FMVSS 213 for car seats, the federal flammability standards for crib mattresses, ASTM/JPMA certifications where they exist — see their application on Newton vs Naturepedic (crib mattresses) or PIPA rx vs KeyFit 35 (car seats) rather than vague reassurance words like "safe" or "tested." Recall status is stated with a check date and database, never as a blanket all-clear. Nothing on this site is medical advice — monitors supplement safe-sleep practice, they never replace it — and where evidence is thin, we say "the manufacturer does not publish this" instead of filling the gap with comforting language.