A marketing director at a 180-person Hong Kong professional services firm has a line in next quarter's budget request that reads "AI search visibility tool". Two names are on the shortlist. Semrush, because the SEO team already knows the brand and the AI Visibility Toolkit is US$99 a month. UDomain AEO Auditor, because a colleague ran the free scan and the site scored 61 out of 172. The CFO has asked one question: what does each one actually do that the other does not?
This page answers that question with current prices, named limits and a verdict per buyer type. It is written for the person who has to justify the line item, not for an SEO specialist.
What decision does this comparison actually settle?
The decision is whether your first AI-visibility spend should go to continuous mention tracking (what Semrush AI Visibility Toolkit does) or to a structural diagnostic of why AI engines can or cannot cite your site (what UDomain AEO Auditor does). They overlap on one module, the AI-readiness site audit, and differ almost everywhere else, including price.
Answer Engine Optimisation (AEO) is the practice of structuring a website and its content so that AI assistants such as ChatGPT, Gemini, Perplexity and Google AI Overviews can read it, trust it and quote it as the answer, with or without a click. AEO tools split into two families: trackers that measure how often AI mentions you, and auditors that diagnose the structural reasons behind that number.
Semrush's product sits firmly in the tracker family. UDomain's sits in the auditor family, with a lighter mention-scan module attached. Choosing between them is therefore less "which is better" than "which job do we need done first".
What is Semrush AI Visibility Toolkit and how much does it cost?
Semrush AI Visibility Toolkit is a standalone subscription that tracks how a brand is mentioned across ChatGPT, Google AI, Gemini and Perplexity. According to Semrush's official pricing page, the Base plan costs US$99 per month per domain, billed annually, and includes 25 tracked prompts with daily AI rankings, one domain for brand performance analysis, AI competitor analysis, prompt research and a site audit for AI readiness.
The published facts, as of 10 September 2026:
--- Price: US$99 per month per domain, billed annually (roughly HK$775 per month or HK$9,300 per year at the pegged rate; HKD figures are approximate).
--- Included: 25 custom prompts tracked daily, 1 domain, AI visibility reports for any domain, 300 AI Analysis reports per day, daily, weekly and monthly data updates.
--- Engines: ChatGPT, Google AI, Gemini, Perplexity.
--- Add-ons: additional users from US$45 per month; Base Report US$10 per month; Pro Report with white-labelling US$20 per month. Third-party reviewer Trakkr (1 September 2026) reports additional domains at US$99 per month each and 50 extra prompts at US$60 per month.
--- Enterprise: custom pricing with unlimited projects, large-scale prompt tracking, SSO, audit logs, a dedicated account manager and an SLA.
--- Trial: Semrush offers a seven-day free trial across its platform; check at sign-up whether the AI Visibility Toolkit is included in the trial you are offered.
The 25-prompt limit is the number to notice. An enterprise with three service lines, each with ten buyer questions, has already exhausted the Base plan before adding a single competitor comparison prompt.
What is UDomain AEO Auditor and how much does it cost?
UDomain AEO Auditor is a free, no-account diagnostic that scans a live URL in about 30 seconds and returns an AI Visibility Score out of 172 structural points, an AI Copy Signals assessment, a brand-mention check across major AI engines and a prioritised action plan. It is built by UD, a Hong Kong technology company operating since 1998, and is available in English, Traditional Chinese, Simplified Chinese, French, Spanish, Japanese and Korean.
The published facts, as of 10 September 2026:
--- Price: HK$0. No credit card, no account. An email address is optional and is used only to show the full dashboard and offer follow-up analysis.
--- Speed: under 30 seconds for most sites; up to 60 seconds for complex sites. Results appear on the page immediately.
--- What it measures: four modules: Overall Score, AI Copy Signals, 11 numeric structure checks and an Action Plan, covering schema markup, AI crawler access, answerability, internal linking, peer comparison and prioritised fixes with expected score impact. Over 170 structural checks in total.
--- Mention scan: a pass/fail check of brand presence across ChatGPT, Gemini, Perplexity and other major AI engines at the moment of scanning, plus a platform-presence read on Reddit, X, YouTube and Wikipedia.
--- Paid path: an optional consultation in which a UD AEO consultant interprets the report and maps an execution roadmap, followed by an implementation engagement if wanted. Consultation and implementation are priced separately; our guide to AEO services pricing in Hong Kong sets out typical audit and retainer ranges.
What the free scan does not do is track your mentions every day. It photographs your structural position and your mention status at one moment, and UD recommends re-scanning monthly.
How do the two tools compare on the criteria that matter to a Hong Kong enterprise?
On the eight criteria a Hong Kong enterprise buyer typically applies, Semrush wins on continuous tracking, prompt volume and historical trend data; UDomain AEO Auditor wins on price, structural diagnostic depth, Chinese-language support and time to a first result; and the two are roughly level on engine coverage and AI-readiness auditing. Neither is a complete answer on its own.
Comparison at a glance
--- Entry price: Semrush US$99 per month per domain, billed annually. UDomain HK$0 for the scan; consultation and implementation quoted separately.
--- Primary job: Semrush tracks how often AI mentions you and your competitors. UDomain diagnoses why AI can or cannot read and cite your site.
--- Engines covered: Semrush lists ChatGPT, Google AI, Gemini and Perplexity. UDomain scans ChatGPT, Google AI Overview, Perplexity, Claude and Gemini for readability and checks mentions across the major engines.
--- Prompt tracking: Semrush tracks 25 custom prompts daily on Base, expandable at US$60 per 50. UDomain has no scheduled prompt tracking; mention status is captured per scan.
--- Historical trend: Semrush stores daily data from the day you subscribe. UDomain relies on you re-scanning monthly and comparing scores.
--- Structural diagnostic: Semrush includes a site audit for AI readiness as one module. UDomain runs 170-plus checks with a prioritised action plan and expected score impact.
--- Chinese-language support: UDomain's interface and report are available in Traditional and Simplified Chinese. Semrush's pricing page does not state Traditional Chinese prompt or interface coverage; verify during the trial.
--- Implementation help: Semrush is a self-serve tool. UDomain offers a consultant-led roadmap and a Hong Kong-based implementation team as a paid option.
Where does Semrush AI Visibility Toolkit win?
Semrush wins wherever the question is "how is our AI visibility trending against competitors, and which prompts are we losing". Daily tracking of 25 named prompts, competitor share-of-voice analysis, prompt research drawn from Semrush's search dataset, and integration with a Pro or Semrush One SEO subscription make it the stronger choice for an in-house SEO team that reports monthly.
Three situations point clearly to Semrush. First, you already pay for Semrush Pro or Guru and want AI visibility in the same dashboard; Semrush One bundles both. Second, you have a defined list of buyer prompts and need a daily time series to show a board that movement is real. Third, you manage multiple brands or regions and need SSO, audit logs and a dedicated account manager, which the Enterprise tier provides at custom pricing.
Semrush also wins on independence of measurement. A tracker measures an outcome, AI mentions, that does not depend on the tracker's own scoring model. An auditor's score is, by construction, the auditor's opinion about structure.
Where does UDomain AEO Auditor win?
UDomain AEO Auditor wins wherever the question is "why does AI not cite us, and what should we fix first". A free scan that returns a 172-point structural score, a named list of failing checks and an action plan ranked by expected impact answers that question in 30 seconds, in Traditional Chinese if you prefer, without a procurement cycle.
Three situations point clearly to UDomain. First, you have no AEO baseline at all and need a number before you can justify any recurring spend; the scan gives you one for HK$0. Second, your site is bilingual or Traditional Chinese-first, and you need the diagnostic to read the Chinese pages as your customers do. Third, you have already decided you will need someone to do the implementation work and want the diagnostic and the implementer to be the same accountable party in Hong Kong.
The auditor also wins on speed of decision. A Semrush subscription is an annual commitment of roughly HK$9,300 before the first data point. A UD scan is a decision you can make between two meetings, and it tells you whether a tracker is even worth buying yet: a site scoring 61 out of 172 has structural work to do before daily mention data becomes meaningful.
What are the limitations of each tool?
Both tools have limits that their own marketing understates. Semrush's Base plan is thin for enterprise use at 25 prompts and one user, is billed annually, and its AI-readiness audit is shallower than a dedicated auditor. UDomain AEO Auditor is a point-in-time diagnostic rather than a monitor, its published uplift figures are UD's own customer aggregates rather than third-party audited, and turning its action plan into results is paid work.
Semrush limitations
--- 25 prompts and one user on Base; additional users from US$45 per month and additional domains at US$99 per month each add up quickly for a multi-brand group.
--- Billed annually. The US$99 monthly figure is a commitment of roughly US$1,188 (about HK$9,300) up front.
--- The site audit for AI readiness is one module among several, not the product's centre of gravity.
--- No Hong Kong or Traditional Chinese coverage is stated on the pricing page; confirm before buying if your customers ask AI in Chinese.
UDomain AEO Auditor limitations
--- It is a diagnostic, not a fix, and not a continuous tracker. A structural score is not a citation; a site can score well and still be absent from answers where authority signals are weak.
--- The "about 80 percent visibility lift" and "up to 3x conversion" figures on the product page are UD's own aggregates from its AEO work, not independently audited benchmarks. Treat them as directional.
--- Structural changes are typically re-crawled within two to four weeks and citation signals take one to three months to accumulate, so the scan cannot show you a result the week after you act.
--- The full dashboard asks for an email address; the consultation and implementation that follow are paid engagements.
For a broader view of where UD sits against dedicated enterprise trackers, our comparison of Profound alternatives for Hong Kong enterprises covers Profound, Peec and Otterly on the same criteria.
Which should a Hong Kong enterprise choose?
Choose by buyer type, not by feature count. Most Hong Kong mid-market enterprises should run the free UDomain scan first to establish a structural baseline, then decide whether Semrush's daily tracking is worth HK$9,300 a year based on what the baseline shows. Organisations with an existing Semrush subscription, a fixed prompt list and monthly board reporting should add the AI Visibility Toolkit and use the free scan only as a periodic structural check.
Verdict by buyer type
--- Marketing director, 50 to 500 staff, no AEO baseline: UDomain AEO Auditor first. Fix the structural failures, re-scan monthly, and revisit a tracker in two quarters.
--- In-house SEO team already on Semrush Pro or Guru: Semrush AI Visibility Toolkit via Semrush One. The integration and time series outweigh the auditor's diagnostic depth for you.
--- Multi-brand group or regional headquarters: Semrush Enterprise or a dedicated tracker such as Profound. The free scan is useful per brand but does not replace governance features.
--- Traditional Chinese-first business serving Hong Kong customers: UDomain AEO Auditor, because the diagnostic reads your Chinese pages and the consultant path is local. Confirm Chinese prompt coverage with Semrush before committing to annual billing.
--- Organisation that already knows it will outsource implementation: UDomain, so that the diagnosis, roadmap and build sit with one accountable Hong Kong partner.
--- Agency reporting to multiple clients: Semrush, for white-labelled Pro Reports and per-client domains, accepting the per-domain cost.
If you want the free-versus-paid decision in more depth, our guide to free AI visibility checkers versus paid trackers explains what US$0 does and does not buy.
What is the correct next step?
Run the free scan on your own domain and on your two closest competitors, which takes under three minutes in total, and put the three scores in the budget request next to the Semrush quote. That single page gives the CFO what they asked for: a number, a comparison and a reason for whichever spend you propose.
If the scores are low and the failing checks are structural, the first money belongs in fixing the structure, whether with your own web team or with a consultant. If the scores are already high and the question is competitive trend, the first money belongs in a tracker. Either way, you have made the decision on evidence rather than on a vendor's feature list.
Conclusion
Semrush AI Visibility Toolkit and UDomain AEO Auditor are not substitutes. One measures the outcome, the other diagnoses the cause. A Hong Kong enterprise that buys the tracker first will watch a flat line without knowing why; one that runs the auditor first will know what to fix but will need a tracker eventually to prove the fix worked.
The honest sequence for most mid-market organisations is diagnostic first, structural fixes second, tracker third. It costs nothing to start, and it turns a vague budget line into a decision your board can follow. We understand AI. We understand you. With UD by your side, AI never feels cold.
Now that you have the comparison, the next step is a baseline you can put in front of your CFO. Run the free scan, then let us walk you through every step, from reading the action plan and prioritising fixes to implementation and monthly re-scans, with a Hong Kong team that has served enterprises for 28 years.
Reviewed by the UD enterprise AI team. Prices and limits verified on 10 September 2026 from Semrush's pricing page, Trakkr's Semrush pricing review (1 September 2026) and the UDomain AEO Auditor product page. HKD conversions are approximate at the pegged rate. Semrush is a trademark of Semrush Holdings; UD has no commercial relationship with Semrush.
