Google Docs , Google Sheets , and Google Slides are a word processor, a spreadsheet and a slideshow presentation program respectively, all part of a free, web-based software office suite offered by Google within its Google Drive service. The three apps are available as web applications , and as mobile apps for Android and iOS . The apps are compatible with Microsoft Office and OpenDocument file formats. The suite also consists of Google Forms (survey software), Google Drawings (diagramming software) and Google Fusion Tables (database manager; experimental  ).
The suite allows users to create and edit files online while collaborating with other users in real-time. Edits are tracked by user with a revision history presenting changes. An editor's position is highlighted with an editor-specific color and cursor. A permissions system regulates what users can do. Updates have introduced features using machine learning , including "Explore", offering search results based on the contents of a document, answers based on natural language questions in a spreadsheet, and dynamic design suggestions based on contents of a slideshow, and "Action items", allowing users to assign tasks to other users.
While Google Docs has been criticized for lacking the functionality of Microsoft Office , it has received praise for its simplicity, ease of collaboration and frequent product updates. Google has been criticized for its practice of automatically scanning documents for keywords that violate the terms of service, and censoring those documents. 
Google Docs originated from two separate products, Writely and XL2Web.
Writely was a web-based word processor created by the software company Upstartle and launched in August 2005.   It began as an experiment by programmers Sam Schillace, Steve Newman and Claudia Carpenter, trying out the then-new Ajax technology and the "content editable" function in browsers.  On March 9, 2006, Google announced that it had acquired Upstartle.  
XL2Web by 2Web Technologies was a web-based spreadsheet application, which was acquired by Google in 2005  and turned into Google Labs Spreadsheets. It was launched as a test for a limited number of users, on a first-come, first-served basis on June 6, 2006.   The limited test was later replaced with a beta version available to all Google Account holders, around the same time as an official announcement press release was issued. 
In January 2010, Google Docs started allowing users to upload any file type up to 250 MB, with 1 GB of free space and paid storage available for $0.25 per GB per year.  This cloud storage feature was eventually reworked when Google Drive was introduced in 2012. Google Drive now serves as the cloud storage service from Google, while Docs, Sheets and Slides serve as the office suite inside Google Drive. 
In March 2010, Google acquired DocVerse, an online document collaboration company. DocVerse allowed multiple user online collaboration on Microsoft Office -compatible document formats such as Word , Excel , and PowerPoint .  Improvements based on DocVerse were announced and deployed in April 2010. 
In October 2012, Google Documents, Spreadsheets and Presentations were renamed Google Docs, Sheets and Slides, respectively. At the same time, Chrome apps were released, which provided shortcuts to the services on Chrome's new tab page.  Google announced in August 2016 that support for Chrome apps would end on Microsoft Windows , Apple macOS , and Linux computers between 2017 and 2018. 
Users can access all documents, spreadsheets and presentations, among other files, collectively through the Google Drive website. In June 2014, Google started rolling out dedicated website homepages for Docs, Sheets and Slides that contain only files created with each respective service. 
In 2015, the mobile websites for Docs, Sheets and Slides were updated with "simpler, more uniform" interfaces for each, and while users can read files through the mobile websites, users trying to edit will be redirected towards the dedicated mobile apps, thus preventing editing on the mobile web. 
Collaboration and revision history
The suite serves as a collaborative tool for cooperative editing of documents, spreadsheets and presentations in real-time. Documents can be shared, opened, and edited by multiple users simultaneously and users are able to see character-by-character changes as other collaborators make edits. Changes are automatically saved to Google's servers, and a revision history is automatically kept so past edits may be viewed and reverted to.  An editor's current position is represented with an editor-specific color/cursor, so if another editor happens to be viewing that part of the document they can see edits as they occur. A sidebar chat functionality allows collaborators to discuss edits. The revision history allows users to see the additions made to a document, with each author distinguished by color. Only adjacent revisions can be compared, and users cannot control how frequently revisions are saved. Files can be exported to a user's local computer in a variety of formats ( ODF , HTML , PDF , RTF , Text , Office Open XML ). Files can be tagged and archived for organizational purposes.
- In Google Docs, Explore shows relevant Google search results based on information in the document, simplifying information gathering. Users can also mark specific document text, press Explore and see search results based on the marked text only.
- In Google Sheets, Explore enables users to ask questions, such as "How many units were sold on Black Friday?", and Explore will return the answer, without requiring formula knowledge from the user.
- In Google Slides, Explore dynamically generates design suggestions based on the contents of each slide.
In December 2016, Google introduced a quick citations feature to Google Docs. The quick citation tool allows users to "insert citations as footnotes with the click of a button" on the web through the Explore feature introduced in September. The citation feature also marked the launch of the Explore functionalities in G Suite for Education accounts.   
In June 2014, Google introduced "Suggested edits" in Google Docs; as part of the "commenting access" permission, participants can come up with suggestions for edits that the author can accept or reject, in contrary to full editing ability. 
In October 2016, Google announced "Action items" to Docs, Sheets, and Slides. If a user writes phrases such as "Ryan to follow up on the keynote script", the respective service will intelligently assign that action to "Ryan". Google states this will make it easier for other collaborators to see which person is responsible for what task. When a user visits Google Drive, Docs, Sheets or Slides, any files with tasks assigned to them will be highlighted with a badge. 
In March 2014, Google introduced add-ons; new tools from third-party developers that add more features for Google Docs and Google Sheets. 
In order to view and edit documents, spreadsheets and presentations offline on a computer, users need to be using the Google Chrome web browser. A Chrome extension , Google Docs Offline , allows users to enable offline support for Docs, Sheets and Slides files on the Google Drive website. 
Supported file formats
Files in the following formats can be viewed and converted to Docs, Sheets or Slides formats: 
- For documents: .doc (if newer than Microsoft Office 95), .docx, .docm .dot, .dotx, .dotm, .html, plain text (.txt), .rtf, .odt
- For spreadsheets: .xls (if newer than Microsoft Office 95), .xlsx, .xlsm, .xlt, .xltx, .xltm .ods, .csv, .tsv, .txt, .tab
- For presentations: .ppt (if newer than Microsoft Office 95), .pptx, .pptm, .pps, .ppsx, .ppsm, .pot, .potx, .potm
- For drawings: .wmf
- For optical character recognition : .jpg, .gif, .png, .pdf
- Documents (Google Docs)
- Up to 1.02 million characters, regardless of the number of pages or font size. Document files converted to .gdoc Docs format cannot be larger than 50 MB. Images inserted cannot be larger than 50 MB, and must be in either .jpg, .png, or non-animated .gif formats.
- Spreadsheets (Google Sheets)
- Up to 2 million cells.
- Presentations (Google Slides)
- Presentation files converted to .gslides Slides format cannot be larger than 100 MB. Images inserted cannot be larger than 50 MB, and must be in either .jpg, .png, or non-animated .gif formats.
The Google Docs, Sheets, and Slides suite is free to use for individuals, but it is also available as part of the business-centered G Suite service by Google, which is a monthly subscription that enables additional business-focused functionality. 
A simple find and replace tool is available.
Google Docs includes a web clipboard tool that allows users to copy and paste content between Google Docs, Sheets, Slides and Drawings. The web clipboard can also be used for copying and pasting content between different computers. Copied items are stored on Google's servers for up to 30 days. For most copying and pasting, Google Docs also supports keyboard shortcuts. 
Google offers an extension for the Google Chrome web browser called Office editing for Docs, Sheets and Slides that enables users to view and edit Microsoft Office documents on Google Chrome, via the Docs, Sheets and Slides apps. The extension can be used for opening Office files stored on the computer using Chrome, as well as for opening Office files encountered on the web (in the form of email attachments, web search results, etc.) without having to download them. The extension is installed on Chrome OS by default. 
Google Cloud Connect was a plug-in for Microsoft Office 2003, 2007 and 2010 that could automatically store and synchronize any Word document, PowerPoint presentation, or Excel spreadsheet to Google Docs (before the introduction of Drive) in Google Docs or Microsoft Office formats. The online copy was automatically updated each time the Microsoft Office document was saved. Microsoft Office documents could be edited offline and synchronized later when online. Google Cloud Connect maintained previous Microsoft Office document versions and allowed multiple users to collaborate by working on the same document at the same time.  
However, Google Cloud Connect has been discontinued as of April 30, 2013, as Google Drive achieves all of the above tasks, with better results. 
Google Forms and Google Drawings
Google Forms is a tool that allows collecting information from users via a personalized survey or quiz. The information is then collected and automatically connected to a spreadsheet. The spreadsheet is populated with the survey and quiz responses. 
The Forms service has also received updates over the years. New features include, but are not limited to, menu search, shuffle of questions for randomized order, limiting responses to once per person, shorter URLs,  custom themes,  automatically generating answer suggestions when creating forms, and an "Upload file" option for users answering to share content through. 
In October 2014, Google introduced add-ons for Google Forms, that enable third-party developers to make new tools for more features in surveys. 
In July 2017, Google updated Forms to add several new features. "Intelligent response validation" is capable of detecting text input in form fields to identify what is written and ask the user to correct the information if wrongly input. Depending on file-sharing settings in Google Drive , users can request file uploads from individuals outside their respective company, with the storage cap initially set at 1 GB , which can be changed to 1 TB . A new checkbox grid enables multi-option answers in a table. In Settings, users can make changes that affect all new forms, such as always collecting email addresses.  
Google Drawings allows users to collaborate creating, sharing, and editing images or drawings. Google Drawings can be used for creating charts, diagrams, designs, flow-charts, etc. It contains a subset of the features in Google Slides but with different templates. Its features include laying out drawings precisely with alignment guides, snap to grid, auto distribution, and inserting drawings into other Google documents, spreadsheets, or presentations. 
In a December 2016 review of the software suite, Edward Mendelsohn of PC Magazine wrote that the suite was "visually elegant" with "effortless collaboration", but that Docs, Sheets and Slides were "less powerful than desktop-based suites". Comparing Google's office suite with Microsoft 's and Apple 's, he stated that "Docs exists only in your Web browser", meaning that users have "more limited feature set" than "the spacious, high-powered setting of a desktop app". He wrote that offline support required a plug-in, describing it as "less convenient than a desktop app, and you have to remember to install it before you need it". Mendelsohn praised the user interface , describing it as "elegant, highly usable" with "fast performance", and that the revision history "alerts you to recent changes, and stores fine-grained records of revisions". Regarding the Explore functionality, he credited it for being the "niftiest new feature" in the suite and that it surpassed comparable features in Microsoft Office. He described the quality of imports of Office files as "impressive fidelity". In summarization, he praised the suite for having "the best balance of speed and power, and the best collaboration features, too", while noting that "it lacks a few features offered by Microsoft Office 365, but it was also faster to load and save in our testing".  In 2011, Paul Sawers of The Next Web described Google Docs as a "pretty robust set of free tools that are improving every month".  In a 2016 review of Google's G Suite business subscription service, Eric Grevstad of PC Magazine stated that Google Docs follows the "80/20" rule: "that is, 80 percent of users will never need more than 20 percent of the features". 
2009 document sharing incident
In early March 2009, a privacy error caused documents to be shared without user consent. Google released a statement, specifying that "sharing was limited to people with whom you, or a collaborator with sharing rights, had previously shared a document". The issue was fixed by Google, and followed by a statement that "less than 0.05% of documents" had been affected by the issue. Furthermore, Google said it has "extensive safeguards in place to protect all documents, and are confident this was an isolated incident". 
However, later the same month, security consultant Ade Barkah wrote on his blog about security issues with the software suite. Issues included that embedded images in private documents could be viewed publicly on the Internet (even after document deletion); when users got access to a document that included a diagram (a new feature at the time), the new user could see any previous version of the diagram (including any sensitive information that was removed before sharing); and in some scenarios, users who had access rights removed from a document could still access the document without the owner's knowledge. Google released a statement that it takes "the security of our users' information very seriously", but "based on the information we've received, we do not believe there are significant security issues with Google Docs". The statement finished with, "We will share more information as soon as it's available."  
2017 phishing incident
In May 2017, a phishing attack impersonating a Google Docs sharing email spread on the Internet. The attack sent emails pretending to be someone the target knew, requesting to share a document with them. Once the link in the email was pressed, users were directed to a real Google account permissions page where the phishing software, a third-party app named "Google Docs", requested access to the user's Google account. Once granted, the software received access to the user's Gmail messages and address book, and sent new fraudulent document invitations to their contacts.  The phishing attack was described by media outlets as "massive"   and "widespread",  and The Next Web ' s Napier Lopez wrote that it's "very easy to fall for".  One of the reasons the attack was so effective was that its email messages passed through spam and security software, and used a real Google address.  Within hours, the attack was stopped and fixed by Google, with a spokesperson stating that "We have taken action to protect users against an email impersonating Google Docs, and have disabled offending accounts. We've removed the fake pages, pushed updates through Safe Browsing, and our abuse team is working to prevent this kind of spoofing from happening again".   On the same day, Google updated Gmail on Android to feature protection from phishing attacks.    Media outlets noticed that, while the added protection was announced on the same day as the attack, it "may not have prevented this week's attack, however, as that attack involved a malicious and fake "Google Docs" app that was hosted on Google's own domain".  In early May 2017, Ars Technica reported that "at least three security researchers" had raised issues about the threat, one of them in October 2011, and that the attacker or attackers behind the actual incident "may have copied the technique from a proof of concept posted by one security researcher to GitHub in February". Furthermore, the report noted that Google had been repeatedly warned by researchers about the potential threat, with security researcher Greg Carson telling Ars Technica that "I don't think Google fully understood how severely this could be abused, but certainly hackers did". 
2017 censorship error
Google uses automated scanning of documents for keywords matching terms that violate the company's terms of service. On October 31, 2017, Google's algorithms started flagging random documents for violating its terms of service. Google recognized this as a bug and stated that blocked documents should be available again. Some media also noted the lack of user control over documents in the cloud.