Communication · United States · USD
Cost to build an app like Slack
A Slack-like app is B2B messaging, and the B2B part changes everything. Workspaces are tenants, admins need controls, IT needs SSO and audit logs, and the buyer will send a security questionnaire before signing. The messaging engine is the visible half; the enterprise layer is the half that closes deals.
What you are actually building
An app like Slack is three or four screens people recognise sitting on a great deal of engineering they never see. These are the screens that define the shape — and the part of each one that costs real money.
The conversation
Delivery receipts, typing, ordering, retries and an offline queue. Sending a message is a distributed-systems problem wearing a text field.
Presence and push
Sockets, presence, silent pushes and reconnection. Background limits and battery decide the design more than the interface does.
Encryption
End-to-end means key exchange, multi-device, backup and recovery — and it rules out server-side search, which changes the product.
Price your own version
The calculator below is preloaded with the Slack template — its features, architecture and a planning scale for year one. Remove what you do not need, add what you do, and the estimate follows.
Building an app like Slack
A starting template, not a specification. Every feature, number and technology choice below is yours to change.
Reference template
Slack
A Slack-like app is B2B messaging, and the B2B part changes everything. Workspaces are tenants, admins need controls, IT needs SSO and audit logs, and the buyer will send a security questionnaire before signing. The messaging engine is the visible half; the enterprise layer is the half that closes deals.
- Preloaded features
- 14
- Category
- Productivity
The conversation
Delivery receipts, typing, ordering, retries and an offline queue. Sending a message is a distributed-systems problem wearing a text field.
Presence and push
Sockets, presence, silent pushes and reconnection. Background limits and battery decide the design more than the interface does.
Encryption
End-to-end means key exchange, multi-device, backup and recovery — and it rules out server-side search, which changes the product.
What makes a Slack-like app expensive
Three things dominate this shape of product. Everything else is comparatively ordinary app development.
Workspace multi-tenancy
Isolated workspaces with their own users, channels, settings, retention policies and billing.
Enterprise requirements
SAML SSO, SCIM provisioning, audit logs, data retention and export, and eventually SOC 2. Non-negotiable above a certain deal size.
The integration platform
Webhooks, bots, slash commands and an app directory. It is what makes the product sticky and it is a public API with all that implies.
Cost breakdown for the default template
Before you change anything. Costed at the midpoint of a $118–$155/hr blended US rate.
Features in a Slack-like app
The starting list, longest build first — each bar is that feature’s share of the biggest one, so you can see where the hours actually go. Every row is a checkbox in the calculator above: this is a template, not a specification.
Core features (10)
511h totalAdvanced features (4)
504h totalIntegrations (5)
- Twilio (SMS & voice)
- Firebase Cloud Messaging
- AWS
- Amplitude / Mixpanel
- Sentry / Datadog (monitoring)
How long, and who builds it
The $688,000–$1,124,000 figure assumes this schedule and this team. Both scale with the answers in the calculator above — and neither is a quote.
Delivery timeline — 9–13 months
- Discovery & product definition4–6 wks
- UI/UX design6–9 wks
- Development (app + backend)21–29 wks
- Integrations & infrastructure6–8 wks
- QA & security testing6–8 wks
- Store submission & launch2–3 wks
The team — 7 people
- Product manager1×
- UI/UX designer1×
- Mobile developer1×
- Backend developer1×
- DevOps / SRE1×½
- QA engineer1×
- Security engineer1×
The phases add to more than the total on purpose: design starts before discovery finishes and QA runs alongside development rather than after it. 7 people is about 6.5 full-time equivalents — a smaller team takes proportionally longer, and a much larger one does not go proportionally faster. The two roles most often missing from a first plan are DevOps and QA, which together are 16% of this build.
Technology considerations
A stack that would serve this product shape well. A recommendation for what you could build — not a claim about what Slack runs.
| Layer | Suggestion |
|---|---|
| Mobile | Native iOS and Android — background delivery, notification reliability and local encrypted storage |
| Backend | Erlang/Elixir or Go for the connection fleet, separate from the HTTP API |
| Database | PostgreSQL for accounts, Cassandra or ScyllaDB for message history |
| Cache | Redis for presence and routing |
| Search | Client-side search where messages are end-to-end encrypted |
| Real-time | Persistent socket fleet with presence, receipts and fan-out |
| Cloud | AWS or GCP |
| Object storage | S3 for encrypted media blobs with short-lived URLs |
| CDN | CloudFront for media fetch |
| Media pipeline | Thumbnailing and compression, done client-side under E2EE |
| Monitoring | Datadog with delivery-latency and socket-churn dashboards |
Top cost drivers
- 1
Medium scale traffic and usage19% of the build
Caching, queues and real monitoring become mandatory. That is real engineering: caching layer (redis or equivalent) in front of hot reads; background job queue for anything slower than a request; read replicas and query-level database tuning. Lower your year-one traffic assumptions and this shrinks immediately.
- 2
Advanced backend architecture10% of the build
Needed when traffic is high enough, or spiky enough, that a single service cannot absorb it and a slow endpoint takes the whole product down with it.
- 3
SOC 2 Type II compliance work4% of the build
Engineering and evidence work to make an audit survivable. Certification fees, legal review and auditor time are separate costs that this estimate excludes.
- 4
5 third-party integrations4% of the build
Every external service is code you write, failure modes you handle and an API that will change without asking you. The ones you can defer are the cheapest scope cuts available.
- 5
Cross-platform + web app3% of the build
Two separate native codebases means the client is built twice. Moving to React Native or Flutter would cut roughly a third of your mobile hours, at the cost of native modules wherever you touch device hardware.
Infrastructure and maintenance
Neither of these is part of the build figure, and neither of them stops.
Cloud infrastructure
$1K – $11K/month
- Baseline environment$120–$420
- Application compute$675–$2,400
- Database$27–$108
- Object storage$105–$130
- CDN & bandwidth$8–$19
- Caching layer$60–$700
Annual maintenance
$103K – $281K/year
15–25% of build cost per year: bug fixes, iOS and Android version updates, SDK and dependency upgrades, security patching and small improvements. Cloud costs are the separate figure alongside.
Building an app like Slack — common questions
How much does it cost to build an app like Slack?
Using this site's default profile — 14 features, cross-platform + web app, a advanced backend and medium scale traffic — the estimate is $688,000 to $1,124,000 for a US team, or roughly 6,476 engineering hours at a blended $118–$155 per hour. That figure covers design, both apps, backend, infrastructure, integrations, security, QA, DevOps and project management. It excludes cloud hosting, vendor fees, marketing and legal. Change any answer in the calculator on this page and the number moves with it.
How long does it take to build an app like Slack?
About 9–13 months with the team this estimate assumes — 7 people, roughly 6.5 full-time equivalents. Discovery and design run first and partly in parallel, development takes about half the calendar, and QA overlaps the back half rather than following it. A smaller team takes proportionally longer; a much larger one does not go proportionally faster, which is why compressing this schedule costs more than it saves below a certain point.
What team do you need to build an app like Slack?
1× product manager, 1× ui/ux designer, 1× mobile developer, 1× backend developer, 1× devops / sre (part-time), 1× qa engineer, 1× security engineer. That is what 6,476 hours of work distributed across 10 disciplines actually requires. The roles people most often leave out of their own plan are DevOps and QA, which together are about 16% of this build.
What does an app like Slack cost to run each month?
Cloud infrastructure is estimated at $1,475 to $10,927 per month at the scale this profile assumes, driven mainly by compute and database. Third-party services add $80 to $4,500. Separately, budget $103,000 to $281,000 a year for maintenance — bug fixes, OS and SDK updates and security patching. None of these are part of the build figure.
What does the enterprise layer cost?
SSO, SCIM, audit logging, retention and export together run 350–500 hours. SOC 2 engineering and evidence work adds around 290 more, before the auditor's fee of $15,000–$45,000.
Is workplace chat a crowded market?
Extremely — as a horizontal product. The viable versions are vertical: messaging built around a specific industry workflow, where the integrations and compliance posture are the differentiator rather than the chat itself.