CtrlK
| Wordtune |
|---|
| Type |
| Developer |
| Initial release |
| Platform |
| Written in |
| Headquarters |
| Users |
| Website |
Wordtune is an artificial intelligence-powered writing and reading assistant developed by AI21 Labs, an Israeli AI company. Launched on October 27, 2020, it was the first commercial product released by AI21 Labs and coincided with the company's public emergence from stealth mode. Wordtune uses proprietary natural language processing models to help users rewrite, rephrase, expand, shorten, and adjust the tone of their text. By 2025, the platform had attracted over 10 million users worldwide and generated more than 782 million rewrite suggestions.
Google named Wordtune one of its favorite Chrome extensions for 2021, recognizing it in the "Communicate and Collaborate" category for its ability to help users rephrase sentences and catch typos across emails and documents.
In April 2025, AI21 Labs halted development of Wordtune to shift its focus toward enterprise AI products, though the service remained accessible to existing users.
AI21 Labs was founded in November 2017 in Tel Aviv, Israel by three co-founders: Amnon Shashua, Yoav Shoham, and Ori Goshen. Shashua is a computer science professor at the Hebrew University of Jerusalem who previously co-founded Mobileye (acquired by Intel for $15.3 billion in 2017) and OrCam Technologies. Shoham is a professor emeritus at Stanford University and a former Google principal scientist who had founded several companies, including Timeful and Katango (both acquired by Google). Goshen is a serial entrepreneur who previously founded Crowdx and worked at Fring, a mobile communication startup with 40 million users.
The company initially operated in stealth mode, developing large language models and researching natural language processing techniques. AI21 Labs built its own proprietary language models, beginning with the Jurassic series, which served as the technological foundation for Wordtune.
On October 27, 2020, AI21 Labs came out of stealth and launched Wordtune as its first consumer product. The tool debuted as a Chrome browser extension that could rewrite and rephrase sentences across any website where a user typed text. At launch, Wordtune offered basic sentence-level rewriting with controls for making text more formal or casual, shorter or longer. Unlike earlier grammar-checking tools such as Grammarly, Wordtune focused specifically on meaning-aware rephrasing rather than surface-level error correction.
The launch attracted significant attention in the AI and productivity tool communities. By the end of 2020, AI21 Labs had raised $25 million in a Series A funding round.
On November 14, 2021, AI21 Labs released Wordtune Read, an AI-powered summarization tool available as both a Chrome extension and a standalone web application. Wordtune Read could process long articles, documents, PDFs, and YouTube video transcripts, condensing them into short, digestible summaries. The feature included a "Spotlight" panel that let users re-summarize a document by focusing on specific topics or keywords, allowing for more targeted analysis.
Also in 2021, Google included Wordtune in its official list of favorite Chrome extensions for the year.
On January 17, 2023, AI21 Labs launched Wordtune Spices, a generative AI feature designed to help writers enhance their content with contextually relevant additions. Spices offered 12 different cues that a writer could use to generate text additions, including:
A key differentiator of Spices was its approach to source attribution. Every factual suggestion generated by Spices included citations traced back to original sources. AI21 Labs published a scientific report alongside the launch, addressing the problem of factual accuracy in AI-generated text. The company described Spices as a tool that enhances human writing rather than replacing it, distinguishing it from open-ended text generators like ChatGPT.
On December 14, 2022, AI21 Labs released Wordtune for iOS, bringing the writing assistant to iPhones and iPads. In May 2023, a major update added text generation capabilities to the mobile app, along with voice-activated prompts through Siri integration. Users could dictate prompts such as "write a Twitter thread about..." or "write an email to my boss asking for..." and receive generated text directly on their mobile devices.
In August 2023, AI21 Labs overhauled Wordtune into an all-in-one generative AI platform for both consumers and enterprise clients. The update transformed Wordtune from a browser extension into a full web-based editor (the Wordtune Editor) with document management capabilities, including a Knowledge Library for organizing uploaded documents and links with tagging, note-taking, and semantic search.
In April 2025, AI21 Labs halted development of Wordtune. The company shifted its strategic focus to enterprise-oriented AI products, particularly its Maestro orchestration platform and its Jamba family of language models. According to reporting by Calcalist, Nvidia entered advanced acquisition talks with AI21 Labs for a deal valued at approximately $2 to $3 billion, with interest centered primarily on AI21's workforce of roughly 200 AI researchers rather than its consumer products. As of early 2026, Wordtune remained accessible, but active development had ceased.
Wordtune offered a suite of AI-powered writing and reading tools. The features were accessible through the browser extension, the Wordtune Editor (a web-based document editor), and the iOS mobile app.
The core feature of Wordtune was sentence-level rewriting. Users could highlight any sentence and receive multiple alternative phrasings that preserved the original meaning while improving clarity, flow, or style. The AI analyzed the full context of surrounding sentences rather than processing each sentence in isolation, producing suggestions that fit naturally within the broader text.
Wordtune provided controls for switching between different writing tones:
| Tone | Description |
|---|---|
| Formal | Converts casual language into professional, polished text suitable for business communications, academic writing, or official documents |
| Casual | Transforms stiff or overly formal text into conversational, approachable language |
| Shorten | Condenses wordy sentences into more concise alternatives while preserving core meaning |
| Expand | Elaborates on brief sentences, adding detail or explanation |
Wordtune identified and corrected grammar, spelling, and punctuation errors. The editor used a color-coded system: red underlines indicated grammar, spelling, or punctuation mistakes, while purple underlines suggested improvements to fluency, vocabulary, or clarity.
By highlighting individual words, users could access context-aware synonym suggestions. Unlike a standard thesaurus, Wordtune's synonym feature considered the surrounding sentence to recommend replacements that maintained both meaning and grammatical correctness.
Wordtune could accept input text in over 10 languages and translate it into English while simultaneously offering rewrite suggestions. Supported input languages included Spanish, Mandarin, Arabic, Hindi, Korean, Hebrew, Russian, German, French, and Portuguese.
The Spices feature provided 12 distinct content-generation cues, each designed to help writers overcome writer's block or enrich their text. Every factual suggestion generated by Spices included source citations from at least five verified references.
| Spice | Function |
|---|---|
| Continue writing | Generates the next logical sentences based on existing text |
| Explain | Adds an explanation or clarification of a concept |
| Give an example | Inserts a relevant example to illustrate a point |
| Make an analogy | Creates an analogy to help readers understand a concept |
| Counterargument | Presents an opposing viewpoint or consideration |
| Define | Provides a definition for a term or concept |
| Emphasize | Strengthens a point with additional supporting language |
| Add a statistic | Inserts a relevant, cited statistic |
| Add a historical fact | Provides a cited historical fact related to the topic |
| Add a joke | Inserts a relevant piece of humor |
| Add a quote | Includes a famous or notable quotation |
| Add a conclusion | Generates a concluding statement or paragraph |
Wordtune's summarization tool could process multiple types of content:
The summarizer allowed users to hover over any paragraph in the summary to see the corresponding section in the original source document.
Added in the August 2023 platform update, the Knowledge Library let users build personal repositories of uploaded documents and saved links. Features included tagging, note-taking, and semantic search across all saved materials.
Wordtune offered pre-built templates for common writing tasks, including LinkedIn posts, professional emails, product descriptions, social media captions, and marketing copy.
Users could enter custom prompts of up to 1,000 characters to generate original content from scratch. The feature allowed regeneration until the user was satisfied with the output.
Wordtune was built on AI21 Labs' proprietary language models. The company developed several generations of models that powered the product over its lifetime.
AI21 Labs released Jurassic-1 in August 2021, a large language model with a token vocabulary exceeding 250,000 entries. Jurassic-2 (J2) followed in March 2023 with improvements in quality, zero-shot instruction-following, reduced latency, and multi-language support. These models formed the backbone of Wordtune's rewriting and generation capabilities.
AI21 Labs later developed the Jamba series of models, which combined transformer architecture with the Mamba state-space model in a Mixture of Experts configuration. Jamba models offered several advantages over pure transformer models:
| Property | Advantage |
|---|---|
| Memory efficiency | 10x more efficient than comparable models like Llama-3 |
| Compute requirements | 30% lower than competitors |
| Context window | 256K tokens (approximately 800 pages of text) |
| Token efficiency | ~30% more text per token than standard tokenizers |
AI21 Labs also released a set of Task-Specific APIs that gave developers programmatic access to the language models behind Wordtune. The API set included five capabilities: paraphrasing, summarization, text recommendation, text segmentation, and grammatical error correction.
Wordtune's Spices feature incorporated a fact-checking pipeline that required verification from at least five independent sources before suggesting any factual information. This approach addressed a common criticism of generative AI tools: the tendency to produce plausible-sounding but inaccurate statements (a problem known as hallucination).
Wordtune was available across several platforms and integrated with many popular writing environments.
The primary distribution channel was a browser extension available for Google Chrome, Microsoft Edge, and Mozilla Firefox. The extension worked across any website where the user typed text, providing inline rewriting suggestions without requiring users to switch tabs or copy-paste text.
Compatible platforms included:
| Platform | Integration |
|---|---|
| Google Docs | Full inline support |
| Gmail | Full inline support |
| Slack | Full inline support |
| Full inline support | |
| Twitter/X | Full inline support |
| Full inline support | |
| WhatsApp Web | Full inline support |
| Microsoft Outlook (web) | Full inline support |
The Wordtune Editor was a standalone web-based document editor at app.wordtune.com. It combined writing, rewriting, summarization, and Spices in a single interface, with document management features including folders and a Knowledge Library.
The Wordtune iOS app, released in December 2022, provided mobile access to writing features. A May 2023 update added text generation with Siri voice prompt integration. Android users could access Wordtune features through the mobile web browser or browser extensions.
Wordtune operated on a freemium model with tiered pricing. As of 2024, the pricing structure was:
| Plan | Monthly Price | Annual Price (per month) | Key Features |
|---|---|---|---|
| Free | $0 | $0 | 10 rewrites/day, 10 Spices/day, basic grammar checks, 3 summaries/day |
| Plus | $13.99 | $6.99 | 30 rewrites/day, 30 AI suggestions/day, 15 summaries/month |
| Unlimited | $19.99 | $9.99 | Unlimited rewrites, AI suggestions, and summaries |
| Business | Custom | Custom | Everything in Unlimited plus brand tone features, centralized billing, team management |
Students, educators, and employees of non-profit or NGO organizations were eligible for a 30% discount on the Plus and Unlimited plans. No credit card was required to sign up for the free tier.
By 2025, Wordtune had attracted over 10 million users globally and generated more than 782 million rewrite suggestions. The tool received generally positive reviews across major platforms:
| Platform | Rating |
|---|---|
| Chrome Web Store | 4.6 / 5 |
| Apple App Store | 4.4 / 5 |
| G2 | 4.6 / 5 (192 reviews) |
| Capterra | 4.4 / 5 (81 reviews) |
| Trustpilot | 4.1 / 5 (548 reviews) |
Reviewers frequently praised Wordtune for its time-saving editing capabilities, intuitive interface, and particular usefulness for non-native English speakers. Common criticisms included the restrictive limits of the free tier and occasional irrelevant rewrite suggestions.
Wordtune competed with several other AI-powered writing tools, each occupying a somewhat different niche in the market.
| Tool | Primary Focus | Key Differentiator |
|---|---|---|
| Wordtune | Rewriting and paraphrasing | Meaning-aware sentence rewriting with source-cited content generation |
| Grammarly | Grammar and style correction | Comprehensive grammar checking with broad platform integration |
| QuillBot | Paraphrasing | Academic-focused paraphrasing with plagiarism checker and citation tools |
| ProWritingAid | Style and readability analysis | In-depth writing reports with genre-specific style checks |
| ChatGPT | General-purpose text generation | Open-ended conversational AI for a wide range of writing tasks |
| Jasper | Marketing copy generation | AI content creation designed specifically for marketing teams |
| Copy.ai | Marketing and sales copy | Workflow automation for go-to-market content creation |
Wordtune differentiated itself from grammar-focused tools like Grammarly by emphasizing whole-sentence rewriting that considered meaning and context, not just surface-level correctness. Compared to open-ended generators like ChatGPT, Wordtune was designed as a collaborative assistant that enhanced human writing rather than generating entire passages from scratch.
Wordtune anonymized all user inputs, ensuring that no text data was linked to any specific account or individual. This approach aimed to protect user privacy while still allowing the AI models to process text for suggestions.
AI21 Labs raised significant venture capital during the period of Wordtune's development:
| Round | Date | Amount | Notes |
|---|---|---|---|
| Series A | November 2020 | $25 million | Coincided with Wordtune launch |
| Series B | July 2022 | $64 million | Expansion of AI research |
| Series C | August 2023 | $155 million | Valued company at $1.4 billion (unicorn status) |
| Series C extension | November 2023 | $208 million total | Extended Series C round |
A widely reported $300 million Series D round in 2025, said to be backed by Google and Nvidia, was later reported by Calcalist to have never been formally closed or reflected in the company's capital structure.