Causality Engine vs Cometly: Server-Side Pixel or No Pixel

The short answer: the ad platforms see only part of each sale. For a Shopify or other ecommerce store that wants to know which channels caused its sales, Causality Engine is the pick. There is nothing to install. One read of the GA4 export you already keep is €99 (pricing, checked on 27 October 2026), and the first finding is on the house at app.causalityengine.ai/start. Cometly's own pricing page heads its plans "Built for B2B SaaS". It sells a first-party pixel with server-side tracking, multi-touch attribution and Conversion API feeds to the ad platforms, priced on pageviews and quoted on a call. Choose Cometly if you sell software or subscriptions and need ads tied to pipeline, Stripe revenue and CRM deals. It also fits if your main problem is sending cleaner conversions back to Meta and Google.

Disclosure: I founded Causality Engine and own it, and this page recommends it. Every claim about it links to Causality Engine's own pages.

Both tools start from that same complaint, and fix it at opposite ends. Cometly adds a pixel and a server feed so more conversions reach the platforms' algorithms. Causality Engine adds nothing to the site and reads what GA4 already recorded. It judges the platforms' claims rather than feeding them.

What to know before the pixel goes in:

1. How the bill is sized. Cometly's pricing FAQ estimates monthly pageviews at about 1.5 times sessions, and fits each plan to pageviews. For example, a store with 40,000 sessions a month comes to 40,000 x 1.5 = 60,000 pageviews by that rule. Causality Engine's comparison page prices a read at €99 whatever your revenue or ad spend.
2. What the tag collects. Cometly's pixel guide puts the pixel in the head of every site you track. It says the pixel captures form opt-ins: first name, last name, email and phone. On Shopify the integration installs the pixel and registers order webhooks for you. GA4 is already on your store, recording sessions under your existing consent setup.
3. Which number you will act on. Cometly's Shopify page offers first-touch, last-touch and multi-touch attribution. Each is a rule for sharing credit. Write down the channel decision you face. Then judge either tool by whether it changes that decision with evidence you can check.

Pixel and server, or export and model

Read from each vendor's pages on 27 October 2026.

Sources: Cometly pricing, pixel guide, Shopify integration, integrations, Cometly terms, Cometly MCP, how it works, Causality Engine terms.

Three things that decide it

Feeding the platforms, or checking them

Cometly's Shopify page describes capturing every order server-side, stitching it to the original ad click and forwarding it to Meta, Google and TikTok through their Conversion APIs. That gives the platforms more conversions to bid on. For many advertisers, that is the problem worth paying to fix. The credit itself still comes from a touch rule. Causality Engine works the other way round. It estimates what sales would have been without each channel, from the converting paths already in GA4. Then it rebuilds last-click from the same file, so you can see the gap (causal attribution).

Pipeline features you may not use

Cometly's home page promises to "tie every ad dollar to closed-won ARR". Its solutions list Stripe revenue attribution, pipeline attribution and CRM and warehouse sync (Cometly home). For a SaaS team those are the point. For a DTC store selling through a checkout, they are part of a product built for someone else's funnel.

Consent, before any new tag

In the EU, storing or reading information on a visitor's device needs consent unless it is strictly necessary. That is Article 5(3) of the ePrivacy Directive. The EDPB's Guidelines 2/2023 treat URL and pixel tracking as within that rule. A pixel that also captures form fields brings personal data into scope. Causality Engine's how-it-works page says it works from GA4 data under the same consent and browser limits as GA4, adding no tag. This is a checklist point, not legal advice.

Prices, checked on 27 October 2026

Cometly's pricing page lists two plans, Core and Enterprise, with no figure: "All plans tailored to fit your existing monthly pageviews", quoted on a 30-minute call. Both bill monthly or annually, with 20% off for annual payment. There is no free trial because, the FAQ says, attribution needs CRM and ad-platform setup to be useful.

Causality Engine's pricing page lists one read at €99, Pro at €299 a month billed monthly with no seat fees, and a custom Enterprise pilot, all excluding VAT. Pro adds automated GA4 ingestion, a lifetime look-back and budget alerts.

What happens when traffic grows

Cometly's pricing FAQ says it never throttles attribution. Once traffic passes 90% of its pageview allowance, it moves an account up a tier at the start of the next billing period. Section 3.7 of its terms calls all fees non-refundable. So growth raises the bill by default, with no decision on your side.

Causality Engine's comparison with Cometly is the company I own describing a rival, so weigh it as such. It names Cometly's strength the same way this page does: cleaner conversion events for in-platform bidding, for SaaS and subscription advertisers.

Choose Causality Engine if your job is

• Deciding where an ecommerce budget goes next, from what each channel caused.
• Getting an answer without adding a tag, a consent question or a server integration.
• Paying per question instead of per pageview.

Choose Cometly if your job is

• Tying ads to trials, demos, pipeline and closed-won revenue through Stripe and your CRM.
• Sending server-side conversions to Meta, Google, LinkedIn, TikTok and others for their bidding.
• Giving AI agents read access to attribution data through MCP, alongside an AI ads manager.

Further reading: the Causality Engine glossary entry and how to run a first read.

A free count, then the read

Cometly has no trial, so run the free test yourself. Take last week's purchases as Meta, Google and TikTok each report them, and add them up. Put the total next to the store's order count for the same week. If the platforms claim more orders than you shipped, that is not your spreadsheet failing. It is double credit, and a pixel that sends the platforms more conversions does not settle it. Then drop the GA4 export on the start page. The privacy policy says the free preview reads the file in your browser without uploading it.

For the per-channel answer, Causality Engine, which I founded, runs the full read for €99 at app.causalityengine.ai/start, refundable within 30 days. It shows what each channel caused, a data-health score and a next step; how it works lists its assumptions. On Pro, ask the chatbot which channel to cut. Then check its answer against the read's receipts before you move money.

FAQ

Does Cometly work for Shopify stores?

Yes. Its Shopify integration installs the pixel, registers order webhooks and attributes each order to campaign, ad set and creative. The rest of its site is written for B2B SaaS.

Does Causality Engine send conversions to Meta or Google?

No. It installs nothing and sends nothing to the ad platforms. It reads a GA4 export and reports back to you. If feeding the platforms is the job, that is what Cometly's Conversion API connections are for.

Can I run both?

Yes. Causality Engine reads a GA4 export, so Cometly's pixel and server feed stay in place. The condition is that GA4 runs on the site, per the home page.