CompareStack/OpenAI API vs Grammarly
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Updated March 2026 · Independent Analysis

OpenAI APIvsGrammarly

OpenAI API is free; Grammarly starts at $12/mo. Both rated 4.8/5 by users.

O
OpenAI API

Developer API platform providing access to GPT-4o, DALL-E 3, Whisper, embeddings, and fine-tuning capabilities.

★ 4.8/5Founded 20202M+ users
Try OpenAI API Free →
G
Grammarly

AI writing assistant for grammar, clarity, and tone — works across all your apps.

★ 4.7/5Founded 200930M+ users
Try Grammarly Free →

⚡ Quick Stats

⭐
Avg Rating
OpenAI API4.8/5
Grammarly4.7/5
🏆 OpenAI API wins
💰
Starting Price
OpenAI APIFree
Grammarly$12/mo
🏆 OpenAI API wins
🔧
Features
OpenAI API12
Grammarly8
🏆 OpenAI API wins
🎁
Free Plan
OpenAI APINo
GrammarlyYes ✓
🏆 Grammarly wins

📊 Ratings Breakdown

O

OpenAI API

4.8/5 avg
G2 Score4.7/5
Capterra Score4.8/5
Overall Avg4.75/5
G

Grammarly

4.7/5 avg
G2 Score4.7/5
Capterra Score4.7/5
Overall Avg4.7/5

⚡ Quick Verdict

Independent analysis based on features, pricing, and user ratings

Choose OpenAI API if you need:
  • ✓ GPT-4o access
  • ✓ DALL-E 3
  • ✓ Whisper speech-to-text
  • ✓ Embeddings
  • ✓ Fine-tuning
Try OpenAI API Free →
Choose Grammarly if you need:
  • ✓ Grammar checking
  • ✓ Plagiarism detection
  • ✓ Tone suggestions
  • ✓ Style improvements
  • ✓ Browser extension
Try Grammarly Free →

🔧 Feature Comparison

OpenAI API uniquely offers GPT-4o access, DALL-E 3, Whisper speech-to-text. Grammarly uniquely offers Grammar checking, Plagiarism detection, Tone suggestions. Both share 0 features.

Feature
OpenAI API
Grammarly
GPT-4o access
✓
✗
DALL-E 3
✓
✗
Whisper speech-to-text
✓
✗
Embeddings
✓
✗
Fine-tuning
✓
✗
Assistants API
✓
✗
Batch API
✓
✗
Vision models
✓
✗
Function calling
✓
✗
JSON mode
✓
✗
Streaming
✓
✗
Enterprise tier
✓
✗
Grammar checking
✗
✓
Plagiarism detection
✗
✓
Tone suggestions
✗
✓
Style improvements
✗
✓
Browser extension
✗
✓
MS Office plugin
✗
✓
Mobile app
✗
✓
Team style guide
✗
✓
Total Features
12
8

💰 Pricing Comparison

OpenAI API is free; Grammarly starts at $12/mo.

O

OpenAI API Plans

Paid plans only

Pay per use
Free
  • • Token-based billing
  • • Free trial credit
  • • All models available
Full OpenAI API pricing breakdown →
G

Grammarly Plans

Free tier available

Free
Free
  • • Basic grammar
  • • Spelling
  • • Punctuation
PremiumBest Value
$12/month
  • • Style suggestions
  • • Tone detection
  • • Plagiarism checker
  • • Full rewrites
Business
$15/month
  • • Team features
  • • Style guide
  • • Analytics
  • • Priority support
Full Grammarly pricing breakdown →
🔔 Get notified when prices change

❓ Frequently Asked Questions

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