Custom GPTs vs Claude Projects vs Gemini Gems: Custom AI Assistant Comparison 2026
Quick Overview
The three major AI platforms now all support custom, tailored versions of their models: Custom GPTs (OpenAI), Claude Projects (Anthropic), and Gemini Gems (Google). Each lets you define instructions, upload knowledge files, and create a specialized assistant without writing code — but they differ significantly in customization depth, sharing options, and ecosystem integration.
We built identical custom assistants on all three platforms — a marketing copywriter, a research assistant, and a customer support agent — to compare the experience.
| Platform | Our Score | Best For | Starting Price |
|---|---|---|---|
| Custom GPTs | 9.0/10 | Breadth of features & GPT Store distribution | $20/mo (ChatGPT Plus) |
| Claude Projects | 8.8/10 | Deep customization & long-context reasoning | $20/mo (Claude Pro) |
| Gemini Gems | 8.2/10 | Google ecosystem integration | $19.99/mo (Gemini Advanced) |
Pick Custom GPTs if you want the widest distribution (GPT Store), action/API capabilities, and a mature creation ecosystem. Pick Claude Projects if you need deep customization, massive context windows (200K+ tokens), and nuanced instruction-following. Pick Gemini Gems if you live in the Google ecosystem (Workspace, YouTube, Gmail, Drive).
Comparison Table
| Feature | Custom GPTs | Claude Projects | Gemini Gems |
|---|---|---|---|
| Custom Instructions | ✅ System prompt (up to 8K chars) | ✅ System prompt (detailed) | ✅ Instructions + suggested prompts |
| Knowledge Files | ✅ Up to 20 files (text, PDF, CSV, etc.) | ✅ File uploads (text, PDF, code) | ✅ Drive integration + file upload |
| Internet Browsing | ✅ Optional toggle | ✅ Optional (Sono) | ✅ By default (Google Search) |
| Image Generation | ✅ DALL-E built-in | ❌ (text-only model) | ✅ Imagen built-in |
| Code Interpreter | ✅ Built-in (Code Interpreter) | ✅ Built-in (Artifacts) | ❌ (can generate, limited exec) |
| Actions/API Calls | ✅ GPT Actions (OpenAPI spec) | ❌ (no external API actions) | ✅ Extension integration |
| Conversation Memory | ✅ Per-session + custom instructions | ✅ Per-session + 200K context | ✅ Per-session + 2M token context |
| Sharing & Publishing | ✅ GPT Store (public) + share links | ❌ (private only, share links) | ✅ Google shared link |
| Private Deployment | ✅ Internal org GPTs | ✅ Project collaboration | ❌ (personal workspace only) |
| Team/Collaborative | ✅ ChatGPT Team/Business | ✅ Claude for Work | ✅ Google Workspace |
| Multimodal Input | ✅ Image, audio, document upload | ✅ Image, document upload | ✅ Image, audio, video, document |
| Ecosystem Integration | ✅ Zapier, API via Actions | ❌ Limited | ✅ YouTube, Drive, Gmail, Maps |
| Max Context Window | ~128K tokens | ~200K tokens | ~2M tokens |
| Free Plan Access | ❌ (Paid-only for creation) | ❌ (Paid-only for Projects) | ❌ (Paid-only for Gems) |
Detailed Head-to-Head
Pricing
Custom GPTs (OpenAI):
- ChatGPT Plus ($20/mo): Create unlimited GPTs, GPT Store access, GPT-4o models
- ChatGPT Team ($25/user/mo, annual): Private GPTs for team workspace, higher usage limits
- ChatGPT Enterprise (Custom): Org-wide GPTs, SSO, analytics, unlimited high-speed access
Claude Projects (Anthropic):
- Claude Pro ($20/mo): Create Projects with custom instructions + knowledge, 200K context
- Claude Team ($25/user/mo): Shared Projects, higher usage limits, collaborative workspaces
- Claude Enterprise (Custom): SSO, centralized billing, expanded context
Gemini Gems (Google):
- Gemini Advanced ($19.99/mo, Google One AI Premium): Create custom Gems, 2M context window, Deep Research
- Gemini Business ($20/user/mo, Workspace add-on): Gems for workplace, integration with Workspace apps
- Gemini Enterprise (Custom): Advanced admin controls, data regions
Customization Depth
Custom GPTs offer the richest customization toolkit. You can write a system prompt (up to ~8000 characters), upload knowledge files (up to 20), enable optional capabilities (browsing, DALL-E, code interpreter), and — most powerfully — add GPT Actions that call external APIs via OpenAPI specs. This means your custom GPT can connect to your CRM, database, or any REST API. A real-estate GPT could query MLS listings. A support GPT could create Zendesk tickets. No other platform offers this level of extensibility.
Claude Projects take a different approach. Instead of actions and external APIs, Claude Projects focus on deep reasoning with your content. You upload knowledge files (whole documents, codebases, research papers) and Claude works with them in a 200K token context. The results are often more nuanced and thoughtful because Claude can process more of your source material simultaneously. The downside: no external API calls, no image generation, and no public distribution channel.
Gemini Gems emphasize ecosystem integration. You set instructions and can connect the Gem to Google services like Google Drive, Gmail, YouTube, Google Maps, and Google Calendar. This makes Gems uniquely powerful for personal productivity. A “Trip Planner” Gem can access your Gmail for flight confirmations, Google Maps for directions, and YouTube for destination videos. The 2 million token context window is the largest of any platform — you can upload your entire Google Drive folder.
Knowledge & Context Handling
Gemini Gems win on raw context capacity with 2 million tokens — enough to process entire collections of documents. Claude Projects offer 200K tokens, which handles most single-project use cases (entire codebases, long research papers, full book manuscripts). Custom GPTs max out at ~128K tokens but compensate with upload flexibility (20 files) and bite-sized knowledge that the model references efficiently.
In practice: If you’re analyzing a 500-page research corpus, use Gemini Gems. If you’re working through a complex codebase, use Claude Projects. If you’re building a customizable assistant for multiple scenarios, use Custom GPTs.
Sharing & Distribution
Custom GPTs have the most mature sharing ecosystem. The GPT Store allows you to publish your GPT publicly, where it can be discovered, used, and rated by other ChatGPT users. You can also share private links. This has spawned a marketplace of niche assistants — writing coaches, coding tutors, travel planners, and more.
Claude Projects remain private. You can share a link that lets others view the Project configuration and use it with their own Claude account, but there’s no public marketplace. Projects are designed for individual productivity and team collaboration, not distribution.
Gemini Gems offers shared links and is working toward a Gems gallery, but in 2026 the ecosystem is less mature than OpenAI’s GPT Store. Google focuses on personal productivity Gems rather than a public marketplace.
Use Cases
For Power Users Building Multi-Tool Assistants (e.g., research→write→image): Custom GPTs lead here. You can build an assistant that researches the web, analyzes uploaded files, writes content, and generates images — all in one conversation. No other platform combines browsing + code interpreter + image generation in a custom assistant.
For Deep Knowledge Work (Research, Analysis, Code Review): Claude Projects excel. Upload your materials, set precise instructions about how Claude should analyze them, and work through complex problems with thoughtful, nuanced responses. The 200K context means you can share an entire project’s worth of documentation.
For Google Workspace Productivity: Gemini Gems are unmatched if you rely on Google services. A Customer Success Gem that reads your Google Drive proposals, checks your Gmail for client context, and drafts personalized emails — all within the Google ecosystem.
For Public Creators & Educators: Custom GPTs with GPT Store distribution are the only option if you want others to discover and use your assistant. Educators have created popular GPTs for lesson planning, quiz generation, and subject tutoring that reach thousands of users.
Limitations
Custom GPTs Limitations:
- Knowledge upload is limited to 20 files — insufficient for large knowledge bases
- GPT Actions require understanding OpenAPI specs (not no-code)
- Free tier users cannot create GPTs — only subscribers
- Conversation quality depends heavily on prompt engineering skill
- Files are not searchable across the full context — retrieved via RAG
Claude Projects Limitations:
- No image generation, no external API actions
- No public marketplace for sharing Projects
- File management can feel less polished than GPTs
- Cannot access real-time data unless you paste it in (browsing is available but limited)
- No code interpreter equivalent (Artifacts is different — previews generated code but doesn’t execute)
Gemini Gems Limitations:
- Customization is less flexible than Custom GPTs or Claude Projects
- No actions/API integration outside Google services
- Gems gallery/marketplace is immature
- Output quality for complex instructions can lag behind GPTs and Claude Projects
- Best Gems require heavy Google ecosystem dependency
Verdict
| Use Case | Winner |
|---|---|
| Public distribution & GPT Store | Custom GPTs |
| Deep knowledge work & analysis | Claude Projects |
| Google ecosystem productivity | Gemini Gems |
| Multi-capability assistant (web + code + image) | Custom GPTs |
| Team/collaborative custom assistants | Claude Projects (for work) |
| Personal productivity assistant | Gemini Gems |
| API-connected smart assistants | Custom GPTs (Actions) |
The smart strategy: Use Custom GPTs for public-facing or API-connected assistants. Use Claude Projects for deep work with specific knowledge bases (code, research, analysis). Use Gemini Gems for personal productivity tied to Google services. Many power users maintain assistants on all three platforms for different contexts.
FAQ
Can I make a Custom GPT that uses my company’s API?
Yes — through GPT Actions. You describe your API in an OpenAPI spec (JSON format), upload it to your GPT’s configuration, and the GPT can make authenticated API calls during conversations. This is powerful for CRM lookups, ticket creation, and database queries.
Are Claude Projects shareable with my team?
Yes. Claude for Work (Team plan at $25/user/mo) includes shared Projects that your entire team can access and contribute to. Projects can be organized by initiative, with custom instructions and files that everyone on the team uses.
What’s the difference between Claude Projects and Claude Artifacts?
Projects are a container for custom instructions, knowledge, and conversations around a specific topic (like a “project folder”). Artifacts are generated content (code, documents, designs) that Claude can create and display in a separate window alongside the conversation. They work together — you can use a Project to set context, and Claude generates Artifacts as output.
Which platform supports the most context?
Gemini Gems with 2 million tokens — enough to upload your entire Google Drive. Claude Projects with 200K tokens handles most practical use cases. Custom GPTs use RAG (Retrieval-Augmented Generation) over uploaded files, effectively referencing knowledge across files without a single massive context window.
Can I generate images inside a custom assistant?
Yes for Custom GPTs (DALL-E integration) and Gemini Gems (Imagen integration). No for Claude Projects — Claude is a text-only model focused on deep reasoning.
Do I need coding skills to create any of these?
No. All three platforms let you create custom assistants entirely through natural language instructions. You describe what the assistant should do and upload reference files. GPT Actions is the only feature that benefits from API knowledge.