Where work happens
Slack is a business communication platform acquired by Salesforce 2021 for $27.7B. Trustpilot: 2.5/5 from 342 reviews. Key complaints: expensive, unreliable notifications, slow loading, broken auth flows. Widely used but polarizing.
Patterns extracted from real user feedback — not raw reviews.
Users are interrupted by Slack notifications once every five minutes on average. The constant pings from multiple channels make it extremely difficult to do focused work. G2 reviews cite 789 mentions of notification issues and 545 mentions of overwhelming notifications in busy channels. Users describe Slack as a 'productivity killer' that creates pressure to respond immediately.
G2 reviews cite 300 mentions of users struggling with inadequate search functionality. Slack is described as an 'information wastebasket' where it's really hard to find information once there's significant traffic. Finding older messages or files is frustrating without exact keywords or channels. People put entire technical requirements in Slack with no way anyone will ever find that information back.
Slack is described as 'super terrible at threading' with threads clearly discouraged in the UX. The problem is that the concept of organizing information neatly by topic 'runs head-on into the rabid bull of real-time chat and everything falls apart.' Threads don't get used effectively in practice, leading to channel chaos and lost context.
Once you upgrade to Enterprise Grid, you're locked in forever. Slack's official position is that Grid's infrastructure is too different to allow downgrades. Downgrading is technically possible but extremely difficult - Grid's data export format is incompatible with Business+ import, and multi-workspace architecture must be collapsed into one workspace. This is intentional vendor lock-in - treat Grid adoption as a permanent decision.
Starting August 2024, Slack began permanently deleting messages and files older than 1 year from free workspaces. Messages older than 90 days are hidden from search. This is a nightmare for compliance, legal, or HR purposes - if you need to reference a conversation from four months ago, it's gone. Upgrading within 1 year recovers hidden messages, but after 1 year, data is permanently lost.
Slack enforces a 9% year-over-year price increase at renewal unless you meet specific conditions: demonstrating 15-20% ARR growth, committing to multi-year contracts, or adding new products. Over four years, this 9% annual uplift adds $38,313 to cumulative costs for a typical deployment - a 38% total increase. Enterprise Grid costs approximately $950K more annually for 5,000 users compared to lower tiers.
Slack AI isn't included in any paid plan - it's a separate add-on costing $10/user/month billed annually. The catch: you must purchase it for all paid users in your workspace, not just those who need it. This 'everyone or no one' setup quickly inflates costs. A 100-person team would pay an extra $12,000/year for AI features.
Slack Pro has a minimum of 3 users required. If you're a team of 2, you still pay for 3 users - that's $21.75/month minimum. Multi-channel guests count as paid users (only single-channel guests are free). The price jump from Pro to Business+ is steep ($7.25 to $15 per user) if you need SSO or AI features.
Slack's memory footprint increases as users sign into more teams, as each team runs in its own webview. Running the app continuously can result in it devouring nearly 4GB of RAM. Users report that if you care about battery life or CPU/memory availability, you shouldn't use Slack desktop with more than one or two accounts. Resource usage increases linearly as you add more accounts.
G2 reviews describe support as 'really, really bad' with emails taking months for a reply. Capterra users report it's hard to reach a human agent and tickets get bounced between departments. Support policies are overly stringent - for example, only the primary workspace owner can approve certain requests even if you're an administrator. Free plan users have no customer support access at all.
Slack encrypts data in transit and at rest but does NOT provide end-to-end encryption. Customer-managed keys are only available via Enterprise Key Management (EKM) on Enterprise+. In July 2024, a significant data breach exposed PII including names, email addresses, user IDs, internal messages, and shared files. Analysis found 17,000+ Slack credentials being sold on hacking forums. 1 in 166 Slack messages contains confidential information.
Mobile notifications on both iOS and Android are notoriously unreliable. Users report delayed notifications due to device power-saving modes, Do Not Disturb conflicts, and poor network connectivity. The Slack mobile app requires constant troubleshooting - clearing cache, disabling hardware acceleration, managing battery optimization settings. Many users miss critical messages on mobile.
2,600+ integrations connect to virtually any work tool
Slack's integration ecosystem is unmatched with 2,600+ apps including Google Drive, Zoom, Trello, Jira, Salesforce, GitHub, and more. This makes it a central hub for work notifications and actions. Companies using non-Microsoft software find Slack's broad integration ecosystem far more valuable than competitors.
Intuitive interface with fast onboarding
Slack's streamlined, intuitive interface allows new team members to be onboarded in minutes versus hours for competitors like Microsoft Teams. The clean design, emoji reactions, and casual tone align well with startup and creative agency cultures.
Real-time collaboration with channels, threads, and huddles
Slack excels at real-time team communication with organized channels, threaded conversations, and quick audio/video huddles. It's particularly strong for remote teams needing instant communication and quick decisions.
Strong uptime and performance for enterprise scale
Slack handles enterprise-scale deployments reliably - IBM deployed Slack to all 350,000 employees. The platform maintains good uptime with rare outages. Enterprise Grid can handle 8,000+ users in a single workspace effectively.
Generous discounts for education and nonprofits (85% off)
Education and nonprofit organizations can get 85% off Pro, Business+, and Enterprise Grid plans through programs like TechSoup. Companies can also typically negotiate 10-20% below list prices, with some achieving even deeper discounts.
Users: Unlimited users
Storage: 5GB total
Limitations: No SSO, No compliance exports, No guest access controls, No custom retention policies, Cannot recover data after 1 year
Users: Minimum 3 users required
Storage: 10GB per user
Limitations: No SSO/SAML, No data exports for compliance, No user provisioning, No audit logs
Users: Per user pricing
Storage: 20GB per user
Limitations: No Enterprise Key Management, No HIPAA compliance, No unlimited workspaces, Cannot downgrade if you later upgrade to Grid
Users: Unlimited workspaces
Storage: 1TB per user
Limitations: Annual commitment required, Cannot downgrade to Business+ ever, Multi-year contracts often required for discounts
Startups and tech companies with diverse tool stacks
Slack's 2,600+ integrations make it ideal for companies using varied SaaS tools. The casual culture, emoji reactions, and streamlined interface fit startup environments well. Onboarding is fast and intuitive.
Salesforce-centric organizations
As a Salesforce product, Slack integrates deeply with the Salesforce ecosystem. If you're already a Salesforce customer, bundling Slack can provide discounts and unified workflows.
Sales teams
Real-time communication essential for sales. Slack Connect for client channels, Salesforce integration, quick deal updates. Sales thrives on instant communication Slack provides.
Customer support teams
Fast internal escalation, integration with Zendesk/Intercom, shared channels with clients. Support teams benefit from Slack's speed and searchable history.
Companies considering Enterprise Grid
Enterprise Grid is a permanent, irreversible decision with no downgrade path. The infrastructure is too different to allow moving back to Business+. Only commit if you're certain you need multi-workspace architecture forever.
Microsoft 365 heavy organizations
If your organization is deeply invested in Microsoft 365, Teams is likely a better fit as it's included in your subscription and integrates more deeply with Microsoft products. 90% of Fortune 500 companies use Teams.
Teams needing message history on a budget
The free plan's 90-day message limit and permanent 1-year data deletion makes Slack unusable for teams that need to reference past conversations. If you can't afford $7.25/user/month, you'll lose critical context and institutional knowledge.
Deep work professionals (developers, writers, designers)
Slack's notification-heavy culture with interruptions every 5 minutes on average destroys focus time. The pressure to respond immediately and constant pings from multiple channels make deep work nearly impossible. Consider async-first tools instead.
Organizations requiring data sovereignty or E2E encryption
Slack does not offer end-to-end encryption. Customer-managed keys (EKM) are only available on Enterprise+ at $45/user/month. Past breaches have exposed internal messages. Not suitable for highly sensitive communications.
Small teams of 1-2 people
The Pro plan requires a minimum of 3 users, so teams of 2 pay for an unused seat. For small teams, the cost doesn't justify the value when simpler tools like Discord or even email would suffice.
Engineering teams needing focus time
Constant notifications destroy deep work. Studies show developers lose 23 minutes per interruption. Engineers report 2+ hours daily lost to Slack noise. Consider async alternatives.
Common buyer's remorse scenarios reported by users.
Teams using the free plan realize too late that messages older than 90 days are hidden and data older than 1 year is permanently deleted. Important decisions, client conversations, and institutional knowledge disappear. By the time they realize, it's often too late to recover everything.
Companies that upgraded to Enterprise Grid for multi-workspace features discover they can never return to Business+ even if their needs change. The migration to Grid is permanent, and they're locked into the most expensive tier forever with 9% annual price increases.
Teams that went all-in on Slack find their employees constantly distracted, unable to do focused work, and experiencing 'Slack anxiety.' The always-on culture created by constant pings leads to burnout and reduced output. Some companies end up implementing 'Slack-free hours' or banning it entirely for deep work.
Companies are surprised when their Slack bill increases 9% year-over-year at renewal without negotiation. Over 4 years, this compounds to 38% more than the original cost. Teams that didn't lock in multi-year deals or commit to growth targets face steadily rising costs.
Organizations paying thousands for Slack realize that Microsoft Teams is included in their existing Microsoft 365 subscription. The switch saves money but requires painful migration of channels, history, and retraining users.
Scenarios where this product tends to fail users.
The free plan's 10 app integration limit fills up quickly with essential tools like Google Drive, Zoom, Trello, and calendar apps. Once exceeded, you must remove integrations or upgrade to Pro, losing functionality.
Messages older than 90 days are hidden on the free plan. If you need to reference a client discussion, policy decision, or technical specification from months ago, it's inaccessible. After 1 year, it's permanently deleted.
SSO is not available on Free or Pro plans - you must upgrade to Business+ at $15/user/month (double the Pro price). For a 100-person company, this means $18,000/year just to get enterprise authentication.
Slack AI requires purchase for ALL paid users in your workspace, not just those who need it. If only 10 of your 100 employees need AI features, you still pay $10/user for all 100 - an extra $12,000/year instead of $1,200.
Once upgraded to Enterprise Grid, there is no downgrade path. Even if your company shrinks, gets acquired, or no longer needs multi-workspace architecture, you're stuck on the most expensive tier indefinitely.
Users managing multiple Slack workspaces find the desktop app consuming 3-4GB+ of RAM, slowing down their entire computer. Each workspace runs in its own webview, compounding resource usage linearly.
Microsoft Teams
Companies switch because Teams is included in Microsoft 365 they already pay for. Gain: $0 extra cost, native Office integration, built-in video calls. Trade-off: clunkier UX, fewer third-party integrations (2,600+ in Slack vs ~700 in Teams).
Discord
Startups and tech teams switch for better free tier and voice features. Gain: unlimited message history free, superior voice channels, screen sharing. Trade-off: less professional appearance, no enterprise compliance.
Mattermost
Organizations switch for self-hosted option, open source codebase, and data sovereignty. Popular with security-conscious companies and those needing on-premise deployment.
Google Chat
Google Workspace users switch because Chat is included in their subscription, integrates with Gmail/Calendar/Drive, and provides adequate functionality without extra cost.
Zulip
Teams prioritizing async work switch for topic-based threading. Gain: conversations organized by topic not time, open source, self-hostable. Trade-off: smaller ecosystem, less polished UI.
