Email is evolving fast. With AI apps rewriting how we work, dozens of solutions promise to revolutionize your inbox. But not all AI is created equal.
Two apps stand out in the race: Superhuman and Spark (commonly searched as "Spark AI" for its powerful AI features). One is built for individuals who want to move at the speed of thought. The other leans into team collaboration and shared inboxes.
We've developed deep insights into what truly makes an email client worth the investment. While most people fixate on Spark having a free tier, we're here to share why Superhuman is far superior for professionals seeking the ultimate email experience.
In this comprehensive guide, we'll compare these apps across speed, AI capabilities, design, value, and real-world use cases — so you can choose the right email app to level up your inbox.
Quick comparison
AI features: In-Depth analysis
Spark AI
Spark's AI feature set (which we'll refer to as "Spark AI" throughout this comparison) delivers a powerful suite of AI writing and productivity features:
- +AI Writing Assistant: Draft emails from scratch based on a prompt or email context.
- Quick Replies: Suggests fast responses, reducing reply time.
- Rephrase: Makes your writing clearer or more concise in one click.
- Proofread: Checks for grammar, spelling, and overall tone.
- Tone Adjustment: Toggle between professional, friendly, or casual.
- Translate: Convert emails into multiple languages, ideal for international teams.
- Summarize: Boil down long threads into brief overviews for faster understanding.
These tools are available directly in the compose window and feel intuitive to use. Spark AI focuses on reducing the effort it takes to craft polished, professional communication — especially helpful for those managing high volumes of outbound and internal email.
Superhuman
Superhuman's AI features are deeply integrated into the experience and tuned for power users:
- Write with AI: Drafts email responses in your voice and tone, learning from your previous conversations.
- Auto Drafts: Prepares follow-ups automatically by referencing your calendar and past messages.
- Ask AI: Enables natural-language search across your inbox. Ask for flights, meetings, attachments, or insights, and Superhuman delivers an instant summary.
- Auto Labels: Categorizes incoming email into action-based groups like 'Needs response,' 'Waiting on,' or 'Meetings.'
- AI Email Summarization: Automatically provides summaries of emails at the top of each message, saving you time parsing through lengthy communications.
What sets Superhuman apart is how the AI "writes in your tone" based on analyzing your previous emails. This is something we use regularly and find invaluable. While we don't rely heavily on AI for writing all emails, the "write in my tone" feature is one we consistently leverage.
Superhuman also takes in far more context from the entire conversation than Spark does. Since Superhuman is a premium product, they can invest more in AI tokens, giving the prompt more context and resulting in higher quality outputs.
Verdict: Spark AI focuses on flexible, contextual writing support. Superhuman focuses on high-speed, deeply personalized productivity. Both are strong — it depends on your workflow, but Superhuman's personalization gives it an edge for professional use.
Design and interface
The aesthetic experience
Superhuman is designed for velocity and beauty. The UI is minimal, elegant, and built to keep you in a state of flow. With every action optimized for keyboard shortcuts, you can reply, archive, and triage email without ever reaching for your mouse.
While Spark's interface is miles better than Gmail or Outlook, it still feels. like email. Superhuman, on the other hand, gives your entire email app a facelift with its beautiful minimal design, consistent colors, fonts, and automatic resizing of emails to make them readable no matter your screen size.
One specific example: in Spark, emails stretch with your screen, making them more difficult to read, while Superhuman sizes your emails perfectly regardless of your screen dimensions. There are no bright, distracting colors — just a beautiful minimal email view that helps you focus on content.
Features like Split Inbox and Auto Labels help you instantly sort what matters. Distractions melt away. You're fully in control.
Organization and structure
Spark AI leans into a traditional UI model. It supports things like inbox delegation and shared threads, but that flexibility comes at a cost. The interface feels busy, with more visual noise and more clicks required to get things done.
While Spark Mail categorizes your emails based on people, newsletters, and notifications, Superhuman allows you to go deeper and categorize emails based on your own preferences into Split Inbox (e.g., emails with a similar subject type, or senders from a specific domain). We use the Split Inbox feature in Superhuman to help us triage similar emails together, reducing the need to context switch.
Verdict: Spark AI is flexible, especially for teams. But for focus, efficiency, and aesthetic experience, Superhuman is in a league of its own.
Speed and productivity: The 4 hour advantage
Superhuman is built for speed. Every aspect of the experience is optimized to help you move faster. Superhuman customers:
- Save 4 hours every week
- Reply 12 hours faster
- Respond to twice as many emails
Features like reminders, keyboard shortcuts, and Split Inbox create a flow state. You can triage 100+ emails in minutes.
Spark AI makes strides with its Smart Inbox, but its performance isn't as snappy. The interface, animations, and tab-switching all create micro-delays. For someone managing dozens or hundreds of daily conversations, those seconds add up.
Try SuperhumanEmail snoozing: natural language Power
A perfect example of Superhuman's speed advantage is email snoozing. With Spark, you can snooze emails, but the ability to write in natural language is nowhere near Superhuman's capabilities.
For instance, in Superhuman, you can snooze until "Next Wednesday at 9 a.m. in Australia". Superhuman automatically does the time conversion for you and allows you to fully write in natural language, while with Spark, you really can only choose from predetermined options like tomorrow or a specific date.
We use natural language multiple times a day when snoozing our emails in Superhuman and can't imagine having guardrails with limited options.
Verdict: Superhuman is the fastest path to inbox zero. Spark AI helps, but doesn't compare when it comes to pure speed and efficiency.
Collaboration and integrations
Superhuman is designed for high-performance individuals and teams who rely on deep tool integration:
- CRM Sync: Connects to HubSpot and Salesforce to manage deals and sequences.
- Team Snippets: Share canned responses and templates.
- Shared Threads: Keep everyone in the loop with clarity, not clutter.
Spark AI excels at team collaboration features:
- Shared Drafts and Comments: Collaborate on email drafts in real time.
- Delegation: Assign messages to teammates with clarity.
- Integrations: Connect with Asana, Trello, Dropbox, and more.
Unified inbox vs separated approach
Spark has a unified inbox, meaning that all of your emails can technically come into one inbox — a feature some people love. It can be helpful if you have multiple work emails and want them all to come into one inbox while still maintaining separate email addresses.
With Superhuman, while you don't have a unified inbox, you can simply jump to another inbox using the keyboard shortcut CTRL 1, 2, 3, etc. On the Superhuman mobile app, swiping through accounts is as easy as clicking your profile icon.
We actually prefer having the inboxes separated as mentally, checking work emails vs personal emails require different mental effort, so even if Superhuman offered this feature, we'd have to think twice before turning it on.
Verdict: Spark AI is better for real-time collaboration inside the inbox. Superhuman is for teams that thrive on speed, structure, and external tools.
Mobile experience
Both apps are available on macOS and iOS. Spark also supports Android.
- Spark AI: Brings most desktop features to mobile, including Smart Inbox and AI writing tools.
- Superhuman: Offers an exceptionally fast and fluid mobile experience. Includes access to Write with AI, Ask AI, and all your inbox tools — so you can triage and respond from anywhere.
Verdict: Spark wins for platform flexibility. Superhuman wins for mobile performance.
Pricing: Investment vs value
Spark AI offers:
- A free tier
- Premium plans from $4.99/month (individuals) to $59.99/month (teams)
Superhuman offers multiple pricing tiers:
- Starter: $25/user/month (billed annually at $300/year) - Includes Email Productivity, Superhuman AI, Team Collaboration, Calendar & Scheduling, and more
- Business: $33/user/month (billed annually at $396/year) - Everything in Starter plus Advanced AI (including Ask AI), Superhuman for Sales, CRM integrations (HubSpot, Salesforce, Pipedrive), Smart Send, and Recent Opens
- Enterprise: Custom pricing - Everything in Business plus Advanced Security & Controls, Single Sign-On, Customer Success Manager, Team Analytics, Priority Support, and VIP Productivity Coaching
While Spark has a free version, Superhuman is positioned as a premium email experience with pricing to match its professional features.
Verdict: Spark AI (the AI-enhanced version of Spark) is more affordable for casual users or budget-conscious teams. Superhuman is a premium investment in speed and productivity that pays dividends for professionals.
Who it's for
Choose Spark AI if:
- You need collaborative features for your team
- You want polished AI writing without investing heavily
- You use Android or prefer a free/low-cost plan
- You're an individual on a budget who wants something better than Gmail/Outlook
Choose Superhuman if:
- You want to fly through your inbox every day
- You rely on personalized AI that learns how you write
- You want deeper integrations with your CRM and other apps
- You're a professional looking for "the best" email experience, regardless of cost
- You value saving time and increasing productivity
Final verdict
Superhuman is the most productive email experience ever made. It helps teams:
- Save 4 hours per person every single week
- Reply to twice as many emails
- Reach inbox zero faster than ever before
Spark AI is a solid, flexible choice for collaboration and clean writing — especially for teams that want to work inside their inbox. But when every second counts and every message matters, Superhuman takes the cake.
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