Spell Check API
Fast English spell checker (US and UK): flags misspellings with ranked suggestions, offsets and an auto-corrected text. Drop-in replacement for the retired Bing Spell Check API (format=bing).
Authentication & base URL
Subscribe through one of our marketplace listings; your marketplace API key and base URL are shown there. All endpoints return JSON over HTTPS, served from a global edge network (typically 20–150 ms).
Endpoints
GET /v1/spellcheck
Check spelling
| Parameter | In | Description | Example |
|---|---|---|---|
text * | query | Text to check (max 20,000 characters) | I recieve alot of emails abuot the the project. |
language | query | en-US (default), en-GB or en (any English). Also accepts mkt=en-US like Bing | en-US |
mode | query | proof (default: spelling + repeated words) or spell (spelling only) | proof |
max_suggestions | query | 1-10 suggestions per error (default 4) | 4 |
words | query | Comma-separated custom words to accept (brand names, jargon) | TidyData,Kubernetes |
ignore_uppercase | query | Skip ALL-CAPS words like acronyms (true/false, default true) | true |
format | query | Leave empty for the full response, or bing for the Bing Spell Check v7 response shape | |
POST /v1/spellcheck
Check spelling (long text in body: plain text, JSON or form field text=)
Request body: text/plain
| Parameter | In | Description | Example |
|---|---|---|---|
language | query | en-US (default), en-GB or en (any English). Also accepts mkt=en-US like Bing | en-US |
mode | query | proof (default: spelling + repeated words) or spell (spelling only) | proof |
max_suggestions | query | 1-10 suggestions per error (default 4) | 4 |
words | query | Comma-separated custom words to accept (brand names, jargon) | TidyData,Kubernetes |
ignore_uppercase | query | Skip ALL-CAPS words like acronyms (true/false, default true) | true |
format | query | Leave empty for the full response, or bing for the Bing Spell Check v7 response shape | |
Example
GET /v1/spellcheck?text=I+recieve+alot+of+emails+abuot+the+the+project+in+paris.&language=en-US
{
"language": "en-US",
"mode": "proof",
"words_checked": 11,
"errors_count": 5,
"corrected": "I receive a lot of emails about the project in Paris.",
"errors": [
{
"offset": 2,
"length": 7,
"token": "recieve",
"type": "UnknownToken",
"suggestions": [
{
"suggestion": "receive",
"score": 0.698
},
{
"suggestion": "relieve",
"score": 0.418
},
{
"suggestion": "revive",
"score": 0.241
},
{
"suggestion": "recipe",
"score": 0.188
}
]
},
{
"offset": 10,
"length": 4,
"token": "alot",
"type": "UnknownToken",
"suggestions": [
{
"suggestion": "a lot",
"score": 0.923
},
{
"suggestion": "allot",
"score": 0.604
},
{
"suggestion": "alto",
"score": 0.604
},
{
"suggestion": "slot",
"score": 0.435
}
]
},
{
"offset": 25,
"length": 5,
"token": "abuot",
"type": "UnknownToken",
"suggestions": [
{
"suggestion": "about",
"score": 0.698
},
{
"suggestion": "abbot",
"score": 0.389
},
{
…Fast English spell checker (US and UK): flags misspellings with ranked suggestions, offsets and an auto-corrected text. Drop-in replacement for the retired Bing Spell Check API (format=bing).
Migrating from Bing Spell Check
Microsoft retired the Bing Spell Check API v7 in August 2025. Send the same text and add format=bing to get the same response shape: {"_type": "SpellCheck", "flaggedTokens": [{"offset", "token", "type", "suggestions": [{"suggestion", "score"}]}]}. mkt=en-US / mode=proof|spell are accepted too.
What you get
- Each error with offset, length, token, type (UnknownToken, Variant, Capitalization, RepeatedToken) and ranked suggestions with a 0-1 score.
corrected: the text with the best suggestion applied, ready to show as "Did you mean...?".- US vs UK spelling (color/colour, organize/organise), proper nouns (paris → Paris), repeated words (the the), fused words (alot → a lot), possessives and contractions.
- Skips URLs, emails, @mentions, #hashtags, code in backticks, camelCase names and acronyms. Add your own words with
words=.
Accuracy and speed
- 167,000-word dictionary (SCOWL, Copyright Kevin Atkinson) plus modern words (influencer, chatbot, livestream, cybersecurity...).
- Tested on Wikipedia's list of 3,900 common misspellings: 99% detected, the right word is the first suggestion 86% of the time and in the top 4 95% of the time.
- Typo-aware ranking (keyboard neighbours, doubled letters, swapped letters) and no AI calls: deterministic, private (texts are not stored) and fast on a global edge network.
Use cases
Forms, comments and chat apps, CMS and email editors, search "did you mean", data cleaning of names and product titles, education apps, SEO content checks.
Pricing
Free plan 500 requests/month, Pro 25,000 for $4.99, Ultra 150,000 for $14.99.
Pricing
Free plan with 500 calls per month, then Pro (25,000 calls for $4.99/month) and Ultra (150,000 calls for $14.99/month). See all plans.