
lemlist
Instantly.ai
Apollo.io
Reply.io
Mailshake
Hunter.io
SmartLead.ai
Snov.io
SYNCDATE
OneCal.io
Calensync
ChronoLink
SyncThemCalendars
Multical
CalendarBridge
SyncGene
lemlist is the #1-ranked sales engagement platform on G2, used by 20,000+ B2B companies to run multichannel outbound at scale. It covers the full outbound workflow in a single tool: a 600M+ contact database, waterfall enrichment (80% email find rate across 8 providers), multichannel sequences (email, LinkedIn, WhatsApp, phone), AI-powered personalization, a complete deliverability stack, unified inbox, and native CRM integrations with HubSpot, Salesforce, and Pipedrive. Founded in 2018, bootstrapped to $50M ARR and profitable.
SYNCDATE is a web application for live two-way Google Calendar synchronization. Connect multiple Google accounts, select which calendars to sync, choose direction (one-way or two-way), and SYNCDATE keeps events aligned automatically in the background.
Built for professionals juggling multiple Google calendars across work, personal, and side-project accounts.
Outlook support with cross-provider sync - coming soon.
lemlist
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SYNCDATE's answer:
SYNCDATE treats sync as silent infrastructure โ it shows proof instead of making promises. Every sync run is logged with stats, every error comes with a deterministic fix step, and every sync can be cleanly reversed with optional event cleanup. Most calendar sync tools are black boxes. SYNCDATE exposes sync health, freshness, and latency so you can verify it's working in seconds, not just hope it is.
SYNCDATE's answer:
A generous free-forever tier (2 accounts, 2 calendars) covers the most common use case at zero cost โ competitors start at $4โ12/mo. Privacy is the default: synced events show as "busy" unless you opt in to detailed copying. And if you ever want to stop, the Clean Exit flow removes all SYNCDATE-created events from your calendars โ no orphaned copies left behind.
SYNCDATE's answer:
SYNCDATE's answer:
SYNCDATE was born from a real problem: juggling multiple Google accounts and constantly getting double-booked because calendars didn't talk to each other. Existing tools were either expensive for what they offered, opaque about what they were doing, or left orphaned events behind when you stopped using them. SYNCDATE was built to be the sync tool we wanted โ minimal, transparent, and safe to turn off.
SYNCDATE's answer:
Next.js (App Router) with TypeScript, PostgreSQL via Drizzle ORM, Redis with BullMQ for background job processing, Google Calendar API with webhook push notifications, and Stripe for billing. Deployed on a Hetzner server behind Cloudflare with a standalone Node.js worker for sync execution. Observability stack uses Grafana, Loki, Prometheus with PagerDuty for alerts.
Instantly.ai - Build your own infinitely scalable cold email outreach system with Instantly.
OneCal.io - Sync Outlook and Google Calendars in real-time, share booking links, and view all your calendars in one view.
Apollo.io - Apolloโs predictive prospecting, sales engagement, and actionable analytics help the teams to reach its full revenue potential.
Calensync - Synchronize your Google, Outlook, and iCalendars instantly, and create scheduling links to easily book events based on your availability
Reply.io - Reply.io is an AI-driven sales engagement platform that automates cold outreach through unlimited mailboxes, converts website traffic into booked meetings with AI Chat, and empowers your team to streamline the entire sales process with AI SDRs.
ChronoLink - Flexibly synchronize events between different calendars. Select and transform events according to your rules. Supports Google, Microsoft (Outlook.com / Exchange Online), Exchange Server, iCalendar/ICS and other systems.