CalDAV · CardDAV · iCalendar · vCard 4.0

Your existing clients. Zero configuration.

Hermers speaks CalDAV and CardDAV natively. Point Apple Calendar, Thunderbird, GNOME Contacts, or any standards-compliant client at your Hermers endpoint and it just works ; no migration, no new tooling, no configuration scripts.

Connect a Calendar →

// NATIVE.ACCESS ZERO CONFIG

The apps you already use. Unchanged.

Standards-compliant clients connect directly to Hermers endpoints with a single URL and your API key as a password. No plugins, no extensions, no migration scripts.

IMAP :993 / SMTP :587 Apple Mail imap.hermes.io · smtp.hermes.io

IMAP :993 / SMTP :587 Thunderbird imap.hermes.io · smtp.hermes.io

IMAP :993 / SMTP :587 Outlook imap.hermes.io · smtp.hermes.io

CalDAV RFC 4791 Apple Calendar cal.hermes.io/dav/calendars/{user}/

CalDAV RFC 4791 GNOME Calendar cal.hermes.io/dav/calendars/{user}/

CalDAV RFC 4791 Thunderbird Calendar cal.hermes.io/dav/calendars/{user}/

CardDAV RFC 6352 Apple Contacts card.hermes.io/dav/contacts/{user}/

CardDAV RFC 6352 GNOME Contacts card.hermes.io/dav/contacts/{user}/

CardDAV RFC 6352 Any DAV Client card.hermes.io/dav/contacts/{user}/

// CALDAV.LAYER RFC 4791

Full iCalendar support. Native sync across platforms.

Hermers parses and materializes iCalendar events, recurring rules, time zones, alarms, and attendees. Subscribe any CalDAV client ; it stays in sync automatically across Google, Outlook, Apple, and any generic CalDAV feed you connect.

RFC 4791 CALDAV

Events, Recurrence & Alarms

Create, update, and delete events using standard iCalendar. Recurring events with RRULE, exceptions, and overrides are fully supported and expanded on query.

VEVENT, VTODO, VALARM ; full iCalendar component support
RRULE expansion with exception date (EXDATE) handling
ATTENDEE and ORGANIZER fields preserved across sync
Time zone normalization across all connected feeds
CalDAV scheduling with iTIP REQUEST and REPLY auto-dispatch
Also accessible via REST, gRPC, and MCP tools

VAVAILABILITY RFC 7953

Unified Free-Busy Cache

Hermers syncs external feeds from Google, Outlook, Apple, and generic CalDAV sources into a single materialized free-busy cache table. Cross-platform availability resolves in under a millisecond.

Connections to Google Calendar, Outlook, Apple iCloud, and generic CalDAV
Materialized busy-block table updated atomically on every feed sync
Query free-busy for multiple participants in a single API call
VAVAILABILITY component surfaced per RFC 7953 on CalDAV endpoints
Cache remains consistent even across provider-side delays and errors
Conflict detection before any appointment is created

Also accessible via REST /v1/calendar gRPC CalendarService MCP hermes_list_events Native CalDAV

// CARDDAV.LAYER RFC 6352

Contact fidelity at vCard 4.0. Lightning-fast search.

Hermers stores raw vCard 4.0 blobs alongside structured field extractions for prefix search. Your contacts remain in full fidelity ; every phone, address, organization, and custom field preserved ; while being instantly queryable without an external search dependency.

VCARD 4.0 RFC 6350

Full-Fidelity Contact Storage

vCard 4.0 blobs stored verbatim. Structured fields extracted at write time for high-performance querying. Nothing is lost in translation.

FN, N, EMAIL, TEL, ADR, ORG, URL, NOTE ; all standard vCard 4.0 fields
Custom X- extension fields preserved in raw blob
Multiple email addresses and phone numbers per contact
Photo and avatar stored as object blob references, not inline
Group membership tracked for shared address books

FULL-TEXT SEARCH

Prefix Search Without Dependencies

Zero-latency prefix search across the entire contact graph without Elasticsearch, Typesense, or any external search service. Results return in milliseconds on large datasets.

Prefix search on name, email, organization, and phone
Full-text search index maintained natively at write time
Weighted relevance: name matches rank above email, email above org
Per-tenant isolation enforced on every search ; no cross-tenant leakage
Also exposed via MCP hermes_search_contacts tool for AI agents

Also accessible via REST /v1/contacts gRPC ContactService MCP hermes_search_contacts Native CardDAV

// STANDARDS RFC VERIFIED

Every protocol to the letter.

Hermers implements DAV standards completely, not partially. If a spec says it's required, it's implemented. No quirks mode, no workarounds, no silent truncation.

// PROTOCOL COMPLIANCE ALL VERIFIED

CalDAV RFC 4791

Full CalDAV server implementation including scheduling extensions. PROPFIND, REPORT, and MKCALENDAR supported. Per-user calendar collections with ACL control.

iCalendar RFC 5545

VEVENT, VTODO, VJOURNAL, VALARM, VTIMEZONE components. RRULE, EXDATE, RDATE for recurrence. Full property set including non-standard X- extensions.

VAVAILABILITY RFC 7953

VAVAILABILITY component for expressing recurring availability windows. Queryable via CalDAV REPORT and the REST availability endpoint.

CardDAV RFC 6352

Full CardDAV server with addressbook-query REPORT, addressbook-multiget, and sync-collection reports. Per-user address book collections.

vCard 4.0 RFC 6350

vCard 4.0 and vCard 3.0 accepted. Stored as raw text blobs with structured field extraction. Zero-loss round-trip for all standard and extension properties.

iTIP RFC 5546

REQUEST, REPLY, CANCEL, COUNTER, and DECLINECOUNTER methods. Auto-dispatch on appointment create, update, and cancel. RSVP tracking per attendee.

// NATIVE CLIENTS

Connect your existing calendar in 60 seconds.

Open your calendar app's account settings, add a CalDAV account, and point it at your Hermers endpoint. Your credentials are your email and API key. No setup scripts.

Get Connection URL →

// PROGRAMMATIC ACCESS

REST, gRPC, and MCP for everything else.

Every DAV capability ; calendar events, contact search, availability queries ; is also exposed via the REST API, gRPC streaming, and MCP tools for agents and backend services.

View API Reference →