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Issue 10832042: Extensions Docs Server: Doc conversion script (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: script/build.py fixes Created 8 years, 4 months ago
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1 <h1 class="page_title">Frequently Asked Questions</h1>
2 <!-- -->
3 <p>
4 If you don't find an answer to your question here,
5 try the
6 <a href="http://code.google.com/chrome/webstore/faq.html">Chrome Web Store FAQ</ a>, the
7 <a href="http://stackoverflow.com/questions/tagged/google-chrome-extension">[goo gle-chrome-extension] tag on Stack Overflow</a>, the
8 <a href="http://groups.google.com/a/chromium.org/group/chromium-extensions">grou p</a>, or the
9 <a href="http://www.google.com/support/chrome_webstore/">store help</a>.
10 </p>
11 <div id="faq-TOC">
12 <h4>General</h4>
13 <ul>
14 <li><a href="#faq-gen-01">What are Google Chrome Extensions?</a></li>
15 <li><a href="#faq-dev-01">How can I set up Chrome for extension development? </a></li>
16 <li><a href="#faq-gen-02">What technologies are used to write extensions for Chrome?</a></li>
17 <li><a href="#faq-gen-03">Are extensions fetched from the web every time the browser is loaded?</a></li>
18 <li><a href="#faq-dev-14">How do I determine which version of Chrome is depl oyed to which channel?</a></li>
19 </ul>
20 <h4>Capabilities</h4>
21 <ul>
22 <li><a href="#faq-dev-02">Can extensions make cross-domain Ajax requests?</a ></li>
23 <li><a href="#faq-dev-03">Can extensions use 3rd party web services?</a></li >
24 <li><a href="#faq-dev-07">Can extensions encode/decode JSON data?</a></li>
25 <li><a href="#faq-dev-08">Can extensions store data locally?</a></li>
26 <li><a href="#faq-dev-04">Can extensions use OAuth?</a></li>
27 <li><a href="#faq-dev-06">Can extensions load DLLs?</a></li>
28 <li><a href="#faq-dev-05">Can extensions create UI outside of the rendered w eb page?</a></li>
29 <li><a href="#faq-interact-chrome">Can extensions listen to clicks on Chrome tabs and navigation buttons?</a>
30 <li><a href="#faq-dev-11">Can two extensions communicate with each other?</a ></li>
31 <li><a href="#faq-dev-13">Can extensions use Google Analytics?</a></li>
32 <li><a href="#faq-dev-15">Can extensions modify chrome:// URLs?</a></li>
33 <li><a href="#faq-open-popups">Can extensions open browser/page action popup s without user interaction?</a></li>
34 <li><a href="#faq-persist-popups">Can extensions keep popups open after the user clicks away from them?</a></li>
35 <li><a href="#faq-lifecycle-events">Can extensions be notified when they are installed/uninstalled?</a></li>
36 </ul>
37 <h4>Development</h4>
38 <ul>
39 <li><a href="#faq-building-ui">How do I build a UI for my extension?</a>
40 <li><a href="#faq-dev-09">How much data can I store in localStorage?</a></li >
41 <li><a href="#faq-dev-10">How do I create an options menu for my application ?</a></li>
42 <li><a href="#faq-dev-12">What debugging tools are available to extension de velopers?</a></li>
43 <li><a href="#faq-dev-16">Why do wildcard matches not work for top level dom ains (TLDs)?</a></li>
44 <li><a href="#faq-management">Why does the management API not fire events wh en my extension is installed/uninstalled?</a></li>
45 <li><a href="#faq-firstrun">How can an extension determine whether it is run ning for the first time?</a></li>
46 </ul>
47 <h4>Features and bugs</h4>
48 <ul>
49 <li><a href="#faq-fea-01">I think I've found a bug! How do I make sure it ge ts fixed?</a></li>
50 <li><a href="#faq-fea-02">I have a feature request! How can I report it?</a> </li>
51 </ul>
52 </div>
53 <h2>General</h2>
54 <h3 id="faq-gen-01">What are Google Chrome Extensions?</h3>
55 <p>
56 Google Chrome Extensions are applications that run inside the
57 Chrome browser and provide additional functionality, integration with third
58 party websites or services, and customized browsing experiences.
59 </p>
60 <h3 id="faq-dev-01">How can I set up Chrome for extension development?</h3>
61 <p>
62 As long as you are using a version of Chrome that supports
63 extensions, you already have everything you need to start writing an
64 extension of your own.
65 You can start by turning on Developer mode.
66 </p>
67 <p>
68 Click the wrench icon
69 <img src="{{static}}/images/toolsmenu.gif" height="29" width="29" alt=""
70 class="nomargin" />
71 and select <b>Extensions</b> from the <b>Tools</b> menu.
72 If there's a "+" next to "Developer mode",
73 click the "+" so it turns into a "-".
74 Now you can reload extensions,
75 load an unpacked directory of files as if it were a packaged extension,
76 and more. For a complete tutorial, see
77 <a href="http://code.google.com/chrome/extensions/getstarted.html">Getting Sta rted</a>.
78 </p>
79 <h3 id="faq-gen-02">What technologies are used to write extensions for Chrome?</ h3>
80 <p>
81 Extensions are written using the same standard web
82 technologies that developers use to create websites. HTML is used as a
83 content markup language, CSS is used for styling, and JavaScript for
84 scripting. Because Chrome supports HTML5 and CSS3, developers can
85 use the latest open web technologies such as canvas and CSS animations in
86 their extensions. Extensions also have access to several
87 <a href="http://code.google.com/chrome/extensions/api_other.html">JavaScript A PIs</a>
88 that help perform functions like JSON encoding and interacting with the
89 browser.
90 </p>
91 <h3 id="faq-gen-03">Are extensions fetched from the web every time the browser i s loaded?</h3>
92 <p>
93 Extensions are downloaded by the Chrome browser upon install, and
94 are subsequently run off of the local disk in order to speed up
95 performance. However, if a new version of the extension is pushed online,
96 it will be automatically downloaded in the background to any users who
97 have the extension installed. Extensions may also make requests for remote
98 content at any time, in order to interact with a web service or pull new
99 content from the web.
100 </p>
101 <h3 id="faq-dev-14">How do I determine which version of Chrome is deployed to wh ich channel?</h3>
102 <p>
103 To determine which version of Chrome is currently available on each
104 of the different platforms, visit
105 <a href="http://omahaproxy.appspot.com">omahaproxy.appspot.com</a>. On that
106 site you will see data in a format similar to:
107 </p>
108 <pre>cf,dev,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
109 cf,beta,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
110 cf,stable,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
111 linux,dev,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
112 linux,beta,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
113 linux,stable,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
114 mac,dev,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
115 mac,beta,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
116 mac,stable,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
117 win,canary,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
118 win,dev,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
119 win,beta,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
120 win,stable,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
121 cros,dev,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####
122 cros,beta,#.#.###.#,#.#.###.#,mm/dd/yy,mm/dd/yy,#####,#####,#####</pre>
123 <p>
124 Each line represents information about a different platform and channel
125 combination. The
126 listed platforms are <code>cf</code> (Google Chrome Frame),
127 <code>linux</code>, <code>mac</code>, <code>win</code>, and
128 <code>cros</code> (Google Chrome OS). The listed
129 channels are <code>canary</code>, <code>dev</code>, <code>beta</code>,
130 and <code>stable</code>.
131 The two four-part numbers after the channel represent the current and previous
132 versions of Chrome deployed to that platform-channel
133 combination. The rest of the information is metadata about when the releases
134 were first pushed, as well as revision numbers associated with each build.
135 </p>
136 <h2>Capabilities</h2>
137 <h3 id="faq-dev-02">Can extensions make cross-domain Ajax requests?</h3>
138 <p>
139 Yes. Extensions can make cross-domain requests. See
140 <a href="http://code.google.com/chrome/extensions/xhr.html">this page</a>
141 for more information.
142 </p>
143 <h3 id="faq-dev-03">Can extensions use 3rd party web services?</h3>
144 <p>
145 Yes. Extensions are capable of making cross-domain Ajax
146 requests, so they can call remote APIs directly. APIs that provide data
147 in JSON format are particularly easy to use.
148 </p>
149 <h3 id="faq-dev-07">Can extensions encode/decode JSON data?</h3>
150 <p>
151 Yes, because V8 (Chrome's JavaScript engine) supports
152 JSON.stringify and JSON.parse natively, you may use these functions in your
153 extensions
154 <a href="http://json.org/js.html">as described here</a> without including
155 any additional JSON libraries in your code.
156 </p>
157 <h3 id="faq-dev-08">Can extensions store data locally?</h3>
158 <p>
159 Yes, extensions can use <a href="http://dev.w3.org/html5/webstorage/">localSto rage</a>
160 to store string data permanently. Using Chrome's built-in JSON
161 functions, you can store complex data structures in localStorage. For
162 extensions that need to execute SQL queries on their stored data,
163 Chrome implements
164 <a href="http://dev.w3.org/html5/webdatabase/">client side SQL databases</a>,
165 which may be used as well.
166 </p>
167 <h3 id="faq-dev-04">Can extensions use OAuth?</h3>
168 <p>
169 Yes, there are extensions that use OAuth to access remote data
170 APIs. Most developers find it convenient to use a
171 <a href="http://unitedheroes.net/OAuthSimple/js/OAuthSimple.js">JavaScript OAu th library</a>
172 in order to simplify the process of signing OAuth requests.
173 </p>
174 <h3 id="faq-dev-06">Can extensions load DLLs?</h3>
175 <p>
176 Yes, using the <a href="npapi.html">NPAPI interface</a>.
177 Because of the possibility for abuse, though, we will review your extension
178 before hosting it in the Chrome Web Store.
179 </p>
180 <h3 id="faq-dev-05">Can extensions create UI outside of the rendered web page?</ h3>
181 <p>
182 Yes, your extension may add buttons to the Chrome browser's user interface.
183 See <a href="browserAction.html">browser actions</a> and
184 <a href="pageAction.html">page actions</a> for more information.
185 </p>
186 <p>
187 An extension may also create popup notifications, which exist outside of the
188 browser window. See the <a href="notifications.html">desktop
189 notifications</a> documentation for more details.
190 </p>
191 <h3 id="faq-interact-chrome">Can extensions listen to clicks on Chrome tabs and
192 navigation buttons?</h3>
193 <p>
194 No. Extensions are limited to listening to the events described in the <a
195 href="api_index.html">API documentation</a>.
196 </p>
197 <h3 id="faq-dev-11">Can two extensions communicate with each other?</h3>
198 <p>
199 Yes, extensions may pass messages to other extensions. See the
200 <a href="messaging.html#external">message passing documentation</a>
201 for more information.
202 </p>
203 <h3 id="faq-dev-13">Can extensions use Google Analytics?</h3>
204 <p>
205 Yes, since extensions are built just like websites, they can use
206 <a href="http://www.google.com/analytics/">Google Analytics</a> to track
207 usage. However, we strongly advise you to modify the tracking code to pull
208 an HTTPS version of the Google Analytics library. See
209 <a href="tut_analytics.html">this tutorial</a> for more information on doing
210 this.
211 </p>
212 <h3 id="faq-dev-15">Can extensions modify chrome:// URLs?</h3>
213 <p>
214 No. The extensions APIs have been designed to minimize backwards
215 compatibility issues that can arise when new versions of the browser are
216 pushed. Allowing content scripts on <code>chrome://</code>
217 URLs would mean that developers would begin to rely on the DOM, CSS, and
218 JavaScript of these pages to stay the same. In the best case, these pages
219 could not be updated as quickly as they are being updated right now.
220 In the worst case, it could mean that an update to one
221 of these pages could cause an extension to break, causing key parts of the
222 browser to stop working for users of that extension.
223 </p>
224 <p>
225 The reason that <a href="override.html">replacing the content</a>
226 hosted at these URLs entirely is
227 allowed is because it forces an extension developer to implement all of the
228 functionality they want without depending on the browser's internal implementa tion
229 to stay the same.
230 </p>
231 <h3 id="faq-open-popups">Can extensions open browser/page action popups without
232 user interaction?</h3>
233 <p>
234 No, popups can only be opened if the user clicks on the corresponding page or
235 browser action. An extension cannot open its popup programatically.
236 </p>
237 <h3 id="faq-persist-popups">Can extensions keep popups open after the user
238 clicks away from them?</h3>
239 <p>
240 No, popups automatically close when the user focuses on some portion of the
241 browser outside of the popup. There is no way to keep the popup open after
242 the user has clicked away.
243 </p>
244 <h3 id="faq-lifecycle-events">Can extensions be notified when they are
245 installed/uninstalled?</h3>
246 <p>
247 No, there are no events an extension can listen to in order to determine
248 whether it has been installed or uninstalled. However, an extension can
249 determine when it has been run for the first time. See <a
250 href="#faq-firstrun">this FAQ entry</a> for information.
251 </p>
252 <h2>Development</h2>
253 <h3 id="faq-building-ui">How do I build a UI for my extension?</h3>
254 <p>
255 Extensions use HTML and CSS to define their user interfaces, so you can use
256 standard form controls to build your UI, or style the interface with CSS,
257 as you would a web page. Additionally, extensions can add
258 <a href="#faq-dev-05">some limited UI elements to Chrome itself.</a>
259 </p>
260 <h3 id="faq-dev-09">How much data can I store in localStorage?</h3>
261 <p>
262 Extensions can store up to 5MB of data in localStorage.
263 </p>
264 <h3 id="faq-dev-10">How do I create an options menu for my application?</h3>
265 <p>
266 You can let users set options for your extension by creating an
267 <a href="http://code.google.com/chrome/extensions/trunk/options.html">options page</a>,
268 which is a simple HTML page that will be loaded when a user clicks the
269 "options" button for your extension. This page can read and write settings
270 to localStorage, or even send options to a web server so that they can be
271 persisted across browsers.
272 </p>
273 <h3 id="faq-dev-12">What debugging tools are available to extension developers?< /h3>
274 <p>
275 Chrome's built-in developer tools can be used to debug extensions
276 as well as web pages. See this
277 <a href="http://code.google.com/chrome/extensions/tut_debugging.html ">tutoria l on debugging extensions</a>
278 for more information.
279 </p>
280 <h3 id="faq-dev-16">Why do wildcard matches not work for top level domains
281 (TLDs)?</h3>
282 <p>
283 You cannot use wildcard match patterns like <code>http://google.*/*</code>
284 to match TLDs (like <code>http://google.es</code> and
285 <code>http://google.fr</code>) due to the
286 complexity of actually restricting such a match to only the desired domains.
287 </p>
288 <p>
289 For the example of <code>http://google.*/*</code>, the Google domains would
290 be matched, but so would <code>http://google.someotherdomain.com</code>.
291 Additionally, many sites do not own all of the TLDs for their
292 domain. For an example, assume you want to use
293 <code>http://example.*/*</code> to match <code>http://example.com</code> and
294 <code>http://example.es</code>, but <code>http://example.net</code> is a
295 hostile site. If your extension has a bug, the hostile site could potentially
296 attack your extension in order to get access to your extension's increased
297 privileges.
298 </p>
299 <p>
300 You should explicitly enumerate the TLDs that you wish to run
301 your extension on.
302 </p>
303 <h3 id="faq-management">Why does the management API not fire events when my
304 extension is installed/uninstalled?</h3>
305 <p>
306 The <a href="management.html">management API</a> was intended to help create
307 new tab page replacement extensions. It was not intended to fire
308 install/uninstall events for the current extension.
309 </p>
310 <h3 id="faq-firstrun">How can an extension determine whether it is running for
311 the first time?</h3>
312 <p>
313 An extension can check to see whether it is running for the first time by
314 checking for the presence of a value in localStorage, and writing the value if
315 it does not exist. For example:
316 </p>
317 <pre>var firstRun = (localStorage['firstRun'] == 'true');
318 if (!firstRun) {
319 localStorage['firstRun'] = 'true';
320 }</pre>
321 <p>
322 Note that this check should be run in a background page, not a content script.
323 </p>
324 <h2>Features and bugs</h2>
325 <h3 id="faq-fea-01">I think I've found a bug! How do I make sure it gets
326 fixed?</h3>
327 <p>
328 While developing an extension, you may find behavior that does not
329 match the extensions documentation and may be the result of a bug in
330 Chrome. The best thing to do is to make sure an appropriate issue
331 report is filed, and the Chromium team has enough information to reproduce
332 the behavior.
333 </p>
334 <p>The steps you should follow to ensure this are:</p>
335 <ol>
336 <li>
337 Come up with a <em>minimal</em> test extension that demonstrates the issue
338 you wish to report. This extension should have as little code as possible
339 to demonstrate the bug&mdash;generally this should be 100 lines of
340 code or less. Many times, developers find that they cannot reproduce their
341 issues this way, which is a good indicator that the bug is in their own
342 code.
343 </li>
344 <li>
345 Search the issue tracker at
346 <a href="http://www.crbug.com">http://www.crbug.com</a> to see whether
347 someone has reported a similar issue. Most issues related to
348 extensions are filed under <strong>Feature=Extensions</strong>, so to
349 look for an extension bug related to the
350 chrome.tabs.executeScript function (for example), search for
351 "<code>Feature=Extensions Type=Bug chrome.tabs.executeScript</code>",
352 which will give you
353 <a href="http://code.google.com/p/chromium/issues/list?can=2&q=Feature%3DExt ensions+Type%3DBug+chrome.tabs.executeScript&colspec=ID+Stars+Pri+Area+Feature+T ype+Status+Summary+Modified+Owner+Mstone+OS&x=mstone&y=area&cells=tiles">
354 this list of results</a>.
355 </li>
356 <li>
357 If you find a bug that describes your issue, click the star icon to be
358 notified when the bug receives an update. <em>Do not respond to the
359 bug to say "me too" or ask "when will this be fixed?"</em>; such updates
360 can cause hundreds of emails to be sent. Add a comment only if you have
361 information (such as a better test case or a suggested fix) that is likely
362 to be helpful.
363 </li>
364 <li>
365 If you found no appropriate bug to star, file a new issue report at
366 <a href="http://new.crbug.com">http://new.crbug.com</a>. Be as explicit
367 as possible when filling out this form: choose a descriptive title,
368 explain the steps to reproduce the bug, and describe the expected and
369 actual behavior. Attach your test example to the report and add
370 screenshots if appropriate. The easier your report makes it for others
371 to reproduce your issue, the greater chance that your bug will be fixed
372 promptly.
373 </li>
374 <li>
375 Wait for the bug to be updated. Most new bugs are triaged within a week,
376 although it can sometimes take longer for an update. <em>Do not reply
377 to the bug to ask when the issue will be fixed.</em> If your bug has not
378 been modified after two weeks, please post a message to the
379 <a href="http://groups.google.com/a/chromium.org/group/chromium-extensions/t opics">
380 discussion group</a> with a link back to your bug.
381 </li>
382 <li>
383 If you originally reported your bug on the discussion group and were
384 directed to this FAQ entry, reply to your original thread with a link
385 to the bug you starred or reported. This will make it easier for others
386 experiencing the same issue to find the correct bug.
387 </li>
388 </ol>
389 <h3 id="faq-fea-02">I have a feature request! How can I report it?</h3>
390 <p>If you identify a feature (especially if it's related to an experimental
391 API) that could be added to improve the extension development experience,
392 make sure an appropriate request is filed in the issue tracker.</p>
393 <p>The steps you should follow to ensure this are:</p>
394 <ol>
395 <li>
396 Search the issue tracker at
397 <a href="http://www.crbug.com">http://www.crbug.com</a> to see whether
398 someone has requested a similar feature. Most requests related to
399 extensions are filed under <strong>Feature=Extensions</strong>, so to
400 look for an extension feature request related to keyboard shortcuts
401 (for example), search
402 for "<code>Feature=Extensions Type=Feature shortcuts</code>",
403 which will give you
404 <a href="http://code.google.com/p/chromium/issues/list?can=2&q=Feature%3DExt ensions+Type%3DFeature+shortcuts&colspec=ID+Stars+Pri+Area+Feature+Type+Status+S ummary+Modified+Owner+Mstone+OS&x=mstone&y=area&cells=tiles">
405 this list of results</a>.
406 </li>
407 <li>
408 If you find a ticket that matches your request, click the star icon to be
409 notified when the bug receives an update. <em>Do not respond to the
410 bug to say "me too" or ask "when will this be implemented?"</em>; such
411 updates can cause hundreds of emails to be sent.
412 </li>
413 <li>
414 If you found no appropriate ticket to star, file a new request at
415 <a href="http://new.crbug.com">http://new.crbug.com</a>. Be as detailed
416 as possible when filling out this form: choose a descriptive title
417 and explain exactly what feature you would like and how you plan to use it.
418 </li>
419 <li>
420 Wait for the ticket to be updated. Most new requests are triaged within a
421 week, although it can sometimes take longer for an update. <em>Do not reply
422 to the ticket to ask when the feature will be added.</em> If your
423 ticket has not been modified after two weeks, please post a message to the
424 <a href="http://groups.google.com/a/chromium.org/group/chromium-extensions/t opics">
425 discussion group</a> with a link back to your request.
426 </li>
427 <li>
428 If you originally reported your request on the discussion group and were
429 directed to this FAQ entry, reply to your original thread with a link
430 to the ticket you starred or opened. This will make it easier for others
431 with the same request to find the correct ticket.
432 </li>
433 </ol>
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