Website change monitoring

Know when any website changes.

Sentinel checks the pages you care about on a schedule, ignores cosmetic churn, and sends one plain-English sentence for every change that matters — by email digest, Slack, or API.

No credit card. The free plan doesn't expire.

Change detected Tue 30 Jun, 09:12
rivalapp.com/pricing
Pro  $29 /mo
Pro  $39 /mo
Sentinel summary

Competitor raised Pro pricing by 34%.

Sent to your morning digest and #competitors on Slack
The output

One email, not forty alerts.

Changes are batched into a daily or weekly digest — a short list of sentences you can read in under a minute. Anything urgent can also go straight to Slack, Discord, or Teams the moment it's confirmed.

Every summary links to the exact before-and-after diff, so you can verify it yourself in one click.

How it works

From pasted URL to plain English.

No selectors to map and no rules to write. Add a page, pick a schedule, and Sentinel handles the rest — here's a typical day for one monitored URL.

09:00
You add a URL
Sentinel fetches the page and stores a baseline snapshot. Plain HTML, JavaScript-rendered apps, and linked PDFs all work.
12:00
A scheduled check runs
The page is fetched again, its readable content extracted and compared against the snapshot. Nothing changed — nothing happens. Most checks end here, silently.
15:00
Noise gets dropped
A footer timestamp ticked over and a promo banner rotated. The noise filter discards both before they ever reach you.
18:00
A real change is found
The AI reads the exact before-and-after text and writes a single sentence describing what changed. The event is stored with a timestamped diff for your records.
08:00 next day
Your digest arrives
One sentence per change, each linked to its diff. If you've connected Slack, Discord, Teams, or the API, the change was already delivered there at 18:00.
Who uses it

Built for people who get blamed when a page changes quietly.

Compliance & regulatory teams

Regulators edit guidance pages without announcements. Sentinel keeps a timestamped record of every change it finds — useful evidence when an auditor asks exactly when you knew.

Watches: regulator rulebooks, guidance pages, government notices, published PDFs.

SEO & ops at agencies and SaaS

An accidental noindex, a rewritten title tag, or a template change can sit unnoticed for weeks. Watch a whole client portfolio and hear about it the day it happens.

Watches: client pages, robots.txt, sitemaps, competitor pricing and changelogs.

Procurement

Supplier terms shift quietly between renewals — a liability cap halves, an SLA weakens, a data-residency clause moves jurisdiction. Know the day it changes, not at signature time.

Watches: supplier T&Cs, SLA pages, data-processing agreements.

Capabilities

What it does, plainly.

The whole feature list fits on one sheet. Every item below is included on every plan, the free one included.

Watches
Any public URL — static pages, JavaScript-rendered apps, and linked PDFs. If a browser can open it without logging in, Sentinel can watch it.
Checks
On the schedule you set per URL. Fast-moving pricing pages can run frequently; a slow supplier T&Cs page can run weekly.
Filters
Cosmetic churn is dropped before it reaches you: timestamps, cookie banners, view counters, rotating ads and promos.
Summarizes
The AI reads the exact changed text — not the whole page — and writes one sentence: what changed, and the detail that matters.
Delivers
A daily or weekly email digest, instant Slack / Discord / Teams webhooks, and a REST API for anything custom.
Keeps
A timestamped history of every detected change with its full diff — exportable, and audit-friendly.
Pricing

Plans differ by one number: how many URLs you watch.

AI summaries, noise filtering, digests, webhooks, and API access come with every plan. There are no feature gates to decode.

Free
$0
3 URLs

For the handful of pages you already re-check by hand. No card, no expiry.

Start free
Starter
$19 /mo
10 URLs

Solo operators and small teams watching a core set of pages.

Start trial
Business
$99 /mo
200 URLs

Agencies and compliance teams monitoring at scale.

Start trial
Paid plans start with a 14-day trial — no card up front. Cancel anytime. Need more than 200 URLs, SSO, or an SLA? Email us
Compare

An honest look at the alternatives.

Change monitoring is an established category and the incumbents are genuinely good tools — Visualping alone serves over two million users. Here's where each is strong, and where Sentinel differs.

Tool Where it's strong Where Sentinel differs
Visualping Pixel-level visual diffing, a browser extension, and the most mature product in the category, with 2M+ users. You still review screenshots and diffs yourself on most plans. Sentinel writes the plain-English sentence for you, on every plan — at a lower price per tier.
Distill.io Fine-grained element targeting and local, in-browser monitoring, with a generous free tier for tinkerers. Distill is built for power users who enjoy configuring selectors. Sentinel needs a URL and nothing else, then tells you what changed in words.
ChangeTower Long-term page archiving and compliance-oriented alerting. Alerts point to raw changes; interpreting them is your job. Sentinel keeps the timestamped archive and adds the one-sentence interpretation.
Sentinel is the newest tool on this list — that's worth knowing before you commit. What it does that the others don't: an AI-written summary of every meaningful change, included from the free plan up, with plans from $0 to $99.
FAQ

Fair questions.

Is monitoring someone else's website legal?
Sentinel only reads publicly accessible pages — the same content your browser sees — at a polite rate, and only pages you explicitly add. It respects robots directives and never bypasses logins or paywalls. You're reading public information you're entitled to read; Sentinel just reads it on a schedule.
How do I know the AI summary is accurate?
Each summary is generated from the exact before-and-after text of the change, not from a summary of the whole page. Every alert links to the full diff and a timestamped snapshot, so the evidence is always one click away. Trust the sentence for triage; verify against the diff when it matters.
Won't I drown in alerts?
The noise filter drops cosmetic churn — timestamps, cookie banners, rotating promos, view counters — before it reaches you, and real changes are batched into one daily or weekly digest. Most checks find nothing and stay silent.
What kinds of pages can it watch?
Any public URL: regulator guidance, pricing pages, supplier T&Cs, government notices, status pages, sitemaps, robots.txt, changelogs, and linked PDFs. JavaScript-rendered apps work too — Sentinel renders the page the way a browser does before diffing it.
How often does it check?
You choose a schedule per URL. A fast-moving competitor pricing page can be checked frequently; a slow supplier terms page can run weekly. You're never paying to over-check pages that rarely change.
Do I need a credit card to try it?
No. The free plan covers 3 URLs with no card and no time limit. Paid plans start with a 14-day trial, also without a card — you only add one if you decide to stay.
How can it be cheaper than the incumbents and still include AI?
Sentinel runs on modern edge infrastructure that costs a fraction of the traditional cloud stacks the older tools were built on, and the AI model used for summaries costs well under a cent per change. The lower price is structural, not promotional — it doesn't expire.

Watch your first three pages free.

Add a URL, get a baseline in seconds, and receive your first summary the next time something real changes.

Create a free account