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For future visitors to this question:

If you are trying to center an image in a div but the image won't center, this could describe your problem:

jsFiddle DEMO of the problem

<div class="col-sm-4 text-center">
 <img class="img-responsive text-center" src="myPic.jpg" />
</div>

The img-responsive class adds a display:block instruction to the image tag, which stops text-align:center (text-center class) from working.

SOLUTION:

<div class="col-sm-4">
 <img class="img-responsive center-block" src="myPic.jpg" />
</div>

jsFiddle of the solution

Adding the center-block class overrides the display:block instruction put in by using the img-responsive class.

Without the img-responsive class, the image would center just by adding text-center class

Update:

Also, you should know the basics of flexbox and how to use it, since Bootstrap4 now uses it natively.

Here is an excellent, fast-paced video tutorial by Brad Schiff

Here is a great cheat sheet

If you are trying to center an image in a div, but the image won't center, this could describe your problem:

JSFiddle Demo of the problem

<div class="col-sm-4 text-center">
 <img class="img-responsive text-center" src="myPic.jpg" />
</div>

The img-responsive class adds a display:block instruction to the image tag, which stops text-align:center (text-center class) from working.

SOLUTION:

<div class="col-sm-4">
 <img class="img-responsive center-block" src="myPic.jpg" />
</div>

JSFiddle demo of solution

Adding the center-block class overrides the display:block instruction put in by using the img-responsive class. Without the img-responsive class, the image would center just by adding text-center class

Also, you should know the basics of flexbox and how to use it, since Bootstrap 4 now uses it natively.

Here is an excellent, fast-paced video tutorial by Brad Schiff

Here is a great cheat sheet

For future visitors to this question:

If you are trying to center an image in a div but the image won't center, this could describe your problem:

jsFiddle DEMO of the problem

<div class="col-sm-4 text-center">
 <img class="img-responsive text-center" src="myPic.jpg" />
</div>

The img-responsive class adds a display:block instruction to the image tag, which stops text-align:center (text-center class) from working.

SOLUTION:

<div class="col-sm-4">
 <img class="img-responsive center-block" src="myPic.jpg" />
</div>

jsFiddle of the solution

Adding the center-block class overrides the display:block instruction put in by using the img-responsive class.

Without the img-responsive class, the image would center just by adding text-center class

###Update:

Also, you should know the basics of flexbox and how to use it, since Bootstrap4 now uses it natively.

Here is an excellent, fast-paced video tutorial by Brad Schiff

Here is a great cheat sheet

For future visitors to this question:

If you are trying to center an image in a div but the image won't center, this could describe your problem:

jsFiddle DEMO of the problem

<div class="col-sm-4 text-center">
 <img class="img-responsive text-center" src="myPic.jpg" />
</div>

The img-responsive class adds a display:block instruction to the image tag, which stops text-align:center (text-center class) from working.

SOLUTION:

<div class="col-sm-4">
 <img class="img-responsive center-block" src="myPic.jpg" />
</div>

jsFiddle of the solution

Adding the center-block class overrides the display:block instruction put in by using the img-responsive class.

Without the img-responsive class, the image would center just by adding text-center class

Update:

Also, you should know the basics of flexbox and how to use it, since Bootstrap4 now uses it natively.

Here is an excellent, fast-paced video tutorial by Brad Schiff

Here is a great cheat sheet

For future visitors to this question:

If you are trying to center an image in a div but the image won't center, this could describe your problem:

jsFiddle DEMO of the problem

<div class="col-sm-4 text-center">
 <img class="img-responsive text-center" src="myPic.jpg" />
</div>

The img-responsive class adds a display:block instruction to the image tag, which stops text-align:center (text-center class) from working.

SOLUTION:

<div class="col-sm-4">
 <img class="img-responsive center-block" src="myPic.jpg" />
</div>

jsFiddle of the solution

Adding the center-block class overrides the display:block instruction put in by using the img-responsive class.

Without the img-responsive class, the image would center just by adding text-center class

For future visitors to this question:

If you are trying to center an image in a div but the image won't center, this could describe your problem:

jsFiddle DEMO of the problem

<div class="col-sm-4 text-center">
 <img class="img-responsive text-center" src="myPic.jpg" />
</div>

The img-responsive class adds a display:block instruction to the image tag, which stops text-align:center (text-center class) from working.

SOLUTION:

<div class="col-sm-4">
 <img class="img-responsive center-block" src="myPic.jpg" />
</div>

jsFiddle of the solution

Adding the center-block class overrides the display:block instruction put in by using the img-responsive class.

Without the img-responsive class, the image would center just by adding text-center class

###Update:

Also, you should know the basics of flexbox and how to use it, since Bootstrap4 now uses it natively .

Here is an excellent, fast-paced video tutorial by Brad Schiff

Here is a great cheat sheet