Side by side
ForthWrite vs Promptfoo
Compare what each tool does, what it costs, and how it fits your workflow.
Designed for
AI email writer that sounds like you.
Evaluate and test LLM prompts automatically.
Primary task
Email writing
Prompt testing
Pricing
Freemium · Free + from $12/mo
Unknown
Pricing details
Free + from $12/mo
Not documented — check the provider
Billing cycle
Monthly
Not documented
API access
Listed as available
Not documented
Platforms
Web, Chrome Extension
Web, CLI
Integrations
Outlook, Chrome, Gmail
Make
Source rating
5.0 / 5 · 1 ratings
4.0 / 5 · 1 ratings
Catalog views
1k
3.6k
Estimated monthly traffic
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Catalog imported
29 Aug 2026
30 Aug 2026
Listed strengths
- Learns your writing style
- Saves significant email time
- Supports multiple AI models
- No training setup required
- Voice accuracy improves over time as more sent emails are collected
- Automated math prompt evaluation
- Provides prompt quality assurance
- Defines custom metrics
- Side-by-side prompt comparisons
- Existing workflow integration capability
Listed limitations
- Limited to Gmail, Outlook
- Model is pre-selected based on tier unless you provide your own API key
- Data Wiping may lose personalization
- Limited weekly drafts on free plan
- Dependence on Chrome/Microsoft Marketplace for extension
- No mobile version
- No multi-language support
- Possibly complex for beginners
- No SDK for integration
- Poor documentation