Definition
A conversion API sends events from your server to ad platforms (for example purchases, leads) to improve measurement when browser tracking is limited.
Example
A purchase event is sent from your server with value, currency, and event ID for deduplication.
How to use it
- Use a stable event ID for deduplication between pixel and server events.
- Send value and currency consistently to support bidding and reporting.
- Validate event volume and match quality after each release.
Common mistakes
- Sending duplicate events without deduplication IDs.
- Omitting consent checks or sending data without legal basis.
Why this matters
This term matters because it affects how you interpret performance and make budget decisions. If you use inconsistent definitions or windows, ROAS/CPA can look "better" while profit gets worse.
Practical checklist
- Write a 1-line definition for "Conversion API (Server Events)" that your team will use consistently.
- Keep the time window consistent (weekly/monthly/quarterly) when comparing trends.
- Segment results (channel/plan/cohort) before drawing big conclusions from blended averages.
- Sanity-check with a related calculator from the same category on MetricKit.
- Read the related guide (e.g., UTM + GA4 attribution: practical tracking for paid ads (without lying to yourself)) for context and common pitfalls.
Where to use this on MetricKit
Calculators
- Paid Ads Funnel Calculator: Model CPM -> CTR -> CVR to estimate CPC, CPA, ROAS, and profit per 1,000 impressions (with margin and variable costs).
- ROI Calculator: Calculate Return on Investment (ROI) for a campaign or project.
- Incrementality Lift Calculator: Estimate incremental conversions, incremental ROAS, and incremental profit from a holdout test.
- Marginal ROAS Calculator: Estimate diminishing returns and find the profit-maximizing ad spend from a simple response curve.
- Target CPA from LTV Calculator: Translate LTV and contribution margin into a target CPA (and break-even CPA) for paid acquisition.
Guides
- UTM + GA4 attribution: practical tracking for paid ads (without lying to yourself): A practical guide to UTMs and GA4: consistent source/medium/campaign tagging, conversion deduplication, and common attribution traps.