Cal.com Problems & Issues
Real user-reported problems, complaints, and limitations for Cal.com. Based on analysis of 10 signals.
Issues by Category
No Microsoft Exchange 2019 support
Cal.com cannot connect to MS Exchange 2019 calendars, which renders the service completely unusable for organizations using current versions of Microsoft Exchange. This is a dealbreaker for many enterprise users.
Microsoft Teams integration frequently breaks
The Microsoft Teams integration shows as connected but core functionality (Teams meeting links) is missing. Emails contain only 'MS Teams' text without actual join links. There's a persistent error banner about reconnecting the calendar with necessary permissions due to changes on Microsoft's end.
Reminder emails don't work properly
Even when meetings are set in advance, reminder settings don't work properly. Users report that either party won't join because there are no reminders sent, leading to missed meetings and lost business opportunities.
Cal Video has connection issues
Users report occasional Cal Video hiccups where starting a meeting shows an error with the video. This requires closing all browser tabs before it connects to the camera, causing awkward delays at the start of important meetings.
Support responses delayed with template replies
Trustpilot 1-star review: 'you wait 3 days for a response, only to get template replies' and feels abandoned for complex issues beyond basic video calls. Company responds to 100% of negative reviews within one week, but resolution quality varies. Support not available weekends.
Billing system issues with incorrect invoicing
Trustpilot 2-star review (Ben): 'invoices were issued to wrong names despite correct company details. Invoices cannot be reissued' and lacks invoice history in-app. Stated: 'the invoicing and billing side makes it unusable for a serious business.' Problematic for EU VAT compliance.
Self-hosting is complex and requires commercial license for enterprise features
GitHub issues document: CLIENT_FETCH_ERROR loop with ALLOWED_HOSTNAMES mismatch, V2-API server fails with 'Workspace @calcom/api-v2 not found', translations don't load, GOOGLE_API_CREDENTIALS parsing fails. Hacker News: 'tricky to install for non-technical users.' CALCOM_LICENSE_KEY required for API v2.
Performance issues and laggy interface
GitHub Issue #23104: 'Local dev crazy slow' - page load 10-12 seconds on high-end machines, goal to reduce by 80%. Trustpilot 1-star: 'everything is laggy'. Self-hosted instances particularly affected during traffic spikes. Cold starts historically up to 30 seconds.
Complex onboarding without clear guidance
Initial setup feels complex for new users with advanced features lacking clear guidance. Users report clicking around to find where settings are located. Step-by-step walkthroughs or tooltips are especially needed for team scheduling, permissions, and advanced booking rules.
Mobile interface needs optimization
The mobile experience could be improved - interface feels small or slightly slow on phones. Settings and advanced options are easier to manage on desktop. A more optimized mobile layout is needed for quick updates on the go.
Regret Patterns
Common reasons users regret choosing Cal.com.
Chose Cal.com for 'free self-hosting' only to discover it requires commercial license
Users attracted by the open-source self-hosting option discover that API v2 and many enterprise features require a commercial license. The free version requires heavy modifications to run independently.
Onboarded team before testing Microsoft integration stability
Teams migrated from Calendly to save money, only to find Microsoft Teams integration frequently breaks, with meeting links missing from confirmation emails. Rolling back after team adoption is painful.
Relied on Cal.com for client meetings and missed appointments due to reminder failures
Users set up reminder workflows expecting them to work like Calendly, but reminders don't send reliably. This leads to missed meetings with clients and lost business opportunities.
EU business hit with compliance issues due to invoice problems
EU businesses discover too late that Cal.com's billing system generates incorrect invoices that can't be reissued. This creates VAT compliance problems and accounting headaches.
When Cal.com Breaks Down
Specific scenarios where Cal.com fails or underperforms.
Organization uses Microsoft Exchange 2019
Cal.com cannot connect to on-premise Exchange 2019 calendars at all. The product becomes completely unusable and the organization must find an alternative immediately.
Team heavily relies on Microsoft Teams video meetings
The Microsoft Teams integration breaks frequently due to authentication token changes on Microsoft's end. Emails go out with 'MS Teams' text but no actual meeting links, causing chaos.
Business scales and needs enterprise compliance
Moving from Teams ($15/user) to Organization ($37/user) is a 147% price increase. Add compliance requirements (SOC 2, HIPAA) and the cost advantage over Calendly disappears.
Self-hosted instance experiences high traffic
Cold start times can balloon to 30 seconds during traffic spikes. Without proper Redis configuration and optimization, the booking experience degrades significantly.
Support needed outside business hours
Cal.com support doesn't operate on weekends. If booking issues arise during a weekend event or conference, you're on your own until Monday.