how to increase font size in UIWebView

Question

how to increase or decrease the UIWebview font size, not using scalePageToFit:NO;

Taras Kalapun · Accepted Answer · 2009-11-24 14:07:52Z

74

I have 2 buttons - A- and A+

@interface
NSUInteger textFontSize;

- (IBAction)changeTextFontSize:(id)sender
{
    switch ([sender tag]) {
        case 1: // A-
            textFontSize = (textFontSize > 50) ? textFontSize -5 : textFontSize;
            break;
        case 2: // A+
            textFontSize = (textFontSize < 160) ? textFontSize +5 : textFontSize;
            break;
    }

    NSString *jsString = [[NSString alloc] initWithFormat:@"document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '%d%%'", 
                          textFontSize];
    [web stringByEvaluatingJavaScriptFromString:jsString];
    [jsString release];
}

answered Nov 24, 2009 at 14:07

Taras Kalapun

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3 Comments

zekel Over a year ago

Be sure to set textFontSize to an initial value (presumably 100) before calling this.

aerique Over a year ago

It is also possible to set ...style.fontSize (or other CSS properties). In my case this meant I didn't have to convert the scale back to a proper font size between sessions.

Chris Comeau Over a year ago

Seems broken in iOS10 on iPad only. Anyone have any fix or alternative? Thanks!

Guru · Accepted Answer · 2013-07-10 13:22:36Z

11

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    NSString *fontSize=@"143";
    NSString *jsString = [[NSString alloc]      initWithFormat:@"document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '%d%%'",[fontSize intValue]];
    [myWebview stringByEvaluatingJavaScriptFromString:jsString];

}

edited Jul 10, 2013 at 13:22

Guru

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answered Jul 10, 2013 at 13:14

Girish Chauhan

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Comments

Louis Gerbarg · Accepted Answer · 2009-02-26 06:08:28Z

9

There is currently no exposed way to directly manipulate the DOM in a UIWebView, nor any convenience methods for handling things like font sizes. I suggest filing Radars.

Having said that. you can modify the font size by changing the CSS, like any other webpage. If that is not possible (you don't control the content) you can write a small javascript function to change the CSS properties in the pages DOM, and execute it by calling:

- (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script;

answered Feb 26, 2009 at 6:08

Louis Gerbarg

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1 Comment

Praveen-K Over a year ago

but if i change the CSS property through javascript, it lost the position where i was reading the content after increase/decrease the font.

BLC · Accepted Answer · 2017-07-27 10:04:47Z

5

Swift 3

public func webViewDidFinishLoad(_ webView: UIWebView) {        
    let textSize: Int = 300
    webView.stringByEvaluatingJavaScript(from: "document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '\(textSize)%%'")
}

Older Swift:

func webViewDidFinishLoad(webView: UIWebView) {
    let textSize: Int = 300

    webView.stringByEvaluatingJavaScriptFromString("document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '\(textSize)%%'")
}

edited Jul 27, 2017 at 10:04

answered Aug 27, 2015 at 11:40

BLC

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3 Comments

JAL Over a year ago

While this code may answer the question, providing additional context regarding why and/or how this code answers the question improves its long-term value.

Ariel Gemilang Over a year ago

Swift 3

webView.stringByEvaluatingJavaScript(from: "document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '\(textSize)%%'")

BLC Over a year ago

Thanks @ArielGemilang. I updated you per your suggestion.

Doolali · Accepted Answer · 2020-01-27 19:43:36Z

3

Swift 5 Update. This is an updated answer from @BLCs suggestion.

Also fixes the double %% in his string.

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    let textSize = 300
    let javascript = "document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '\(textSize)%'"
    webView.evaluateJavaScript(javascript) { (response, error) in
        print()
    }
}

answered Jan 27, 2020 at 19:43

Doolali

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1 Comment

iPhone 7 Over a year ago

it's perfect answer

johnny · Accepted Answer · 2017-04-12 22:12:06Z

2

in my case im using a UISlider for the fontSize, can be any float value

func webViewDidFinishLoad(_ webView: UIWebView) {

    if let fontSize: Float = (self.fontSizeSlider?.value) {
        webView.stringByEvaluatingJavaScript(from: "document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '\(fontSize)%%'")
        print(fontSize)
    }

}

answered Apr 12, 2017 at 22:12

johnny

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Comments

Hiren · Accepted Answer · 2013-06-19 10:35:26Z

1

Try the below code :

NSString *setTextSizeRule = [NSString stringWithFormat:@"addCSSRule('body', '-webkit-text-size-adjust: %d%%;')",currentTextSize];
[_webview stringByEvaluatingJavaScriptFromString:setTextSizeRule];

answered Jun 19, 2013 at 10:35

Hiren

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Comments

DavidNg · Accepted Answer · 2013-08-25 22:42:03Z

1

Here is mine for changing font size and color in UIWebView:

 NSString *myString=@"Hello World!";
 int textFontSize=2;
 NSString *myHTML=[NSString stringWithFormat: @"<html><body><script>var str = '%@'; document.write(str.fontsize(%d).fontcolor('green'));</script></body></html>",myString,textFontSize];    
 [myWebView loadHTMLString:myHTML baseURL:nil];

answered Aug 25, 2013 at 22:42

DavidNg

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Comments

Rajesh Loganathan · Accepted Answer · 2014-05-22 12:32:34Z

1

Try this simple method

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    int fontValue = 150;
    NSString *webviewFontSize = [NSString stringWithFormat:@"addCSSRule('body', '-webkit-text-size-adjust: %d%%;')",fontValue];
    [your_webview stringByEvaluatingJavaScriptFromString:webviewFontSize];
}

answered May 22, 2014 at 12:32

Rajesh Loganathan

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1 Comment

coder Over a year ago

This is not working for iOS 10.1.1 on iPad, is there any alternative?

Jack · Accepted Answer · 2020-11-10 15:59:02Z

1

In SWIFT -

let fontSize = 20
let fontSetting = "<span style=\"font-size: \(fontSize)\"</span>"
webView.loadHTMLString( fontSetting + myHTMLString, baseURL: nil)

edited Nov 10, 2020 at 15:59

answered Mar 5, 2019 at 10:19

Jack

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Comments

Nupur Sharma · Accepted Answer · 2017-01-27 07:02:12Z

Change the font size of the fetched HTML data by changing the occurrence of font size in the fetched html string to your required font size (40 in this example) in a method.

strHtml = [self htmlEntityDecode:strHtml];//parsing the html string


-(NSString *)htmlEntityDecode:(NSString *)string
{    
string = [string stringByReplacingOccurrencesOfString:@"14px;"   withString:@"40"];
string = [string stringByReplacingOccurrencesOfString:@"15px;"   withString:@"40"];
string = [string stringByReplacingOccurrencesOfString:@"16px;"   withString:@"40"];
string = [string stringByReplacingOccurrencesOfString:@"17px;"   withString:@"40"];
string = [string stringByReplacingOccurrencesOfString:@"18px;"   withString:@"40"];
string = [string stringByReplacingOccurrencesOfString:@"19px;"   withString:@"40"];
string = [string stringByReplacingOccurrencesOfString:@"20px;"   withString:@"40"];

 return string;
}

So the html string: span style='font-size: 20px; Becomes: span style='font-size: 40

Note: Change the other occurrences like gt;, apos; too to get the desired string to load in your Webview.

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