See your free time right on any booking page.
Open-Slot overlays your real Google Calendar availability onto Calendly, Cal.com and other scheduling pages. The slots you're actually free for light up green — pick the right time in one glance, with zero tab-switching.
30 Minute Meeting
Stop flipping between tabs to find a time
When someone sends a scheduling link, you bounce between their page and your calendar — guessing, second-guessing, and occasionally double-booking. Open-Slot puts the answer right where you're already looking.
The old way
- ↔Flip back and forth between the booking page and Google Calendar.
- ?Squint and guess whether 2:00 is actually free — or already taken.
- !Pick a slot that collides with a meeting, then reschedule over email.
- ⏳Lose minutes every single time a new link lands in your inbox.
With Open-Slot
- ✓Your free slots light up green directly on the booking page.
- ✓A floating badge shows how many openings you have today.
- ✓Pick the right time in one glance — no tab-switching at all.
- ✓Highlights update live as your calendar changes.
Up and running in three clicks
No backend, no account to create, no passwords to hand over. Connect once and every supported booking page just works.
Connect Google Calendar
One click, read-only access via Chrome's built-in sign-in. No password, no account, no backend server to trust.
Choose what counts as busy
Pick which calendars to sync, set your working hours, choose a scope (Today / This week / 14 / 30 / 60 days), and your slot length.
Open any booking page
Your free slots light up instantly on Calendly, Cal.com and more — and update automatically as your calendar changes.
Everything you need to book the right slot
Thoughtful details that make finding your free time feel effortless — and keep your calendar private.
Free-slot highlighting
Your open times light up right on the booking page. Highlight color, opacity, and pattern — solid, striped, or border — are all configurable.
Floating "X free today" badge
A small pill near the booking card tells you how many openings you have today — so you always know your day at a glance.
Popup command center
A donut showing % free today, your next free slot, working hours, and a week-at-a-glance strip — your whole day in one tidy view.
Cache-first sync
Fast and resilient: works from cached availability when you're offline or the network is degraded, with smart retry and backoff.
Private by design
Availability is computed locally on your device. OAuth tokens are never stored, there's no Open-Slot server, and calendar access is read-only.
Make it yours
Working hours, weekly schedule, time zone, scope, slot length, and highlight appearance are all fully customizable.
Your calendar never leaves your device.
Open-Slot was built privacy-first. It only ever requests read-only access, computes everything locally, and has no server to send your data to. Here's exactly what that means.
- ✓ Read-only Google Calendar access
- ✓ Availability computed 100% on-device
- ✓ OAuth tokens never persisted to storage
- ✓ No Open-Slot backend server
- ✓ Manifest V3 + hardened CSP, dependency-audited
- ✓ Accessibility audited (WCAG / axe)
- ✓ Localized in English & Spanish
- ✓ The page owner never sees your availability
Tune it to match how you work
Every detail bends to your preferences — from the exact green of your highlights to which days count as working days.
- ◐Highlight appearance — color, opacity, and pattern (solid, striped, or border).
- ⏱Working hours & weekly schedule — set the windows that actually count as available.
- ▦Scope & slot length — Today, this week, or 14 / 30 / 60 days, at the granularity you book.
- ⌖Time zone & calendars — choose which calendars mark you busy and which zone to display.
How people use Open-Slot
Representative examples of the kind of person Open-Slot is built for.
"Clients send me Calendly links all day. Now I just see which of their times I'm free for — green means go. No more accidental double-bookings."
"I book demos off Cal.com constantly. The little 'free today' badge means I never have to open my own calendar in another tab again."
"It's the privacy story that sold me — read-only, nothing leaves my machine. It just quietly highlights my open slots and gets out of the way."
Questions, answered
Is Open-Slot free?
Do I need to create an account?
Is my calendar data safe?
Will the person whose booking page I'm on see my availability?
Which booking sites are supported?
Does it work with Outlook or iCloud?
See your open time at a glance
Add Open-Slot to Chrome and let your free slots light up the next time a booking link lands in your inbox.
Add to Chrome — Free