Slack vs Zoho Cliq

Slack brings all your communication together in one place. It's real-time messaging, archiving and search for modern teams. Create open channels for the projects, groups and topics that the whole team shares. Slack searches whole conversations, not just individual messages, so you can find what you’re looking for no matter who said what or when they said it. Slack free open-source (self-hosted) alternatives are: Mattermost, Rocket.Chat, Zulip
Zoho Cliq
Zoho Cliq combines content and communications into a single view to give you a comprehensive picture of your team's work. Zoho cliq is designed to let information flow freely to bring about that much required transparency to work.
Face to face in the news:

2017 - Zoho Cliq - more secure alternative to free Slack

Zoho quietly refactored its old service Zoho Chat and rolled out new shiny groupchat Zoho Cliq - an alternative to popular Slack. It allows to create multiple teamwork channels, share pictures, files, locations, code snippets. Mobile apps are also available. And of course Zoho wanted to get an advantage over Slack by means of free version. But the problem is that Slack also provides free version for unlimited users. So Zoho focused on security. Free Zoho Cliq version provides security & data retention policies, Google sign-on, two factor authentication, SAML-based single sign-on (SSO), user provisioning and de-provisioning. Though other Slack's free version limitations are retained: 5Gb of space and 10K searchable message history.

2015 - Slack launches a new plan for larger companies to catch up with Zoho Cliq

Collaboration chat app Slack launched some new features that target teams needing help with single sign-on, compliance exports, a 99.99 percent uptime guarantee and 24/7 premium support. It's called a Plus plan, a new option priced at $12.50 per user per month. The companies that will benefit from the Plus plan have specific team management, security and/or compliance requirements, according to Slack officials. These are often larger organizations, they said. Before today there were two options with Slack: Lite, which was free and had some restrictions, and Standard.