Credit goes to SMW Central

Question: What is an IPS file?
Answer: An IPS file is a patch containing (for instance) a hack. By patching this file to an unmodified ROM image of SMW, you will get the hack which lies in the IPS patch.

Question: Why use IPS files instead of ROMs?
Answer: Because giving away ROM files is illegal. The IPS file contains the differences between the original game and your hack. In other words, the IPS file only contains the changes you made to the ROM. Nothing else. Thanks to IPS files, hacks can be given away legally.

Question: This hack of Super Mario World is an IPS file. How do I play this?
Answer: Use the IPS file to patch an unmodified ROM image of Super Mario World. Your ROM must match the ROM with which the hacker created the IPS file.
Most IPS files for SMW require a HEADERED image of the AMERICAN (U) version of Super Mario World. If you use a headerless image, then most IPS files will not work. However, a few IPS files require a different version of Super Mario World, like SMAS+SMW. If the patch has a README file, then read it!

Question: How do I patch a ROM with an IPS file?
Answer: First, you'll need an IPS program. I suggest Lunar IPS, which can be found here. http://fusoya.eludevisibility.org/lips/
Then, you need an unchanged ROM image of SMW. Make a copy of the ROM, rename it to what the hack is called, open Lunar IPS program and click on "Apply IPS Patch". Choose the IPS file and then the copy you just made of the ROM.

Question: How do I create an IPS patch?
Answer: You'll need an IPS program here too (read above). Open Lunar IPS and click on "Create IPS Patch". Choose an UNMODIFIED ROM of Super Mario World. After that, choose your hack. Finally, choose a file name for the patch.
Choose an unmodified ROM that matches your hack. If you made a hack of SMAS+SMW, then choose an unmodified ROM of SMAS+SMW, not a ROM of SMW.

Question: How do I know if my SMW ROM is unmodified?
Answer: Download SMW - Clean Rom Verifier. Or just use the online Clean Rom Verifier, which is located in the Online Tools Section. Either one can verify that your ROM is an unmodified and headered image of the American version of Super Mario World.

Question: What is the hash of a clean ROM of SMW?
Answer: For a headered American (U) image:
SHA1 = 553cf42f35acf63028a369608742bb5b913c103f
RMD160 = cf9460d92ec6ea480599e328de88e80e4a7a054c
For a headerless American (U) image:
SHA1 = 6b47bb75d16514b6a476aa0c73a683a2a4c18765
RMD160 = 65a79144be9966be643b5db06980821a02347177

Question: How do I know if my ROM of SMW is headered or headerless?
Answer: Check the size of your ROM image.
524800 bytes => headered ROM of SMW
524288 bytes => headerless ROM of SMW
Most IPS files for SMW require the headered ROM of 524800 bytes.

Question: What is the difference between a headered ROM and a headerless ROM?
Answer: These are two different formats for ROM images. A headerless ROM only contains the ROM banks in the order from the SNES address space. A headered ROM contains the same ROM banks, but has 512 extra bytes at the start of the file. These 512 bytes form a SMC header and are not part of the cartridge ROM. Most emulators ignore and skip the SMC header.
If you patch an IPS file for a headered ROM to a headerless ROM, or for a headerless ROM to a headered ROM, then the IPS file patches the wrong part of the ROM.

Question: How do I convert a headerless ROM to headered?
Answer: Use a hex editor or other tool to insert 512 bytes at the beginning of the ROM file. To pass the online Clean ROM Verifier, you must start with the American version of SMW, the first byte must be '40', and the remaining 511 bytes must be '00'.

Question: I patched the IPS file to a matching ROM, so why does it not play in the emulator?
Answer: At least one IPS program produces bad files. Try a different IPS program. Most IPS files for Super Mario World expand the size of the ROM to 1, 2 or 4 megabytes. Check that the patched ROM is larger than the unmodified ROM.
Also, some old emulators have bugs. Try a newer emulator.
Also, some IPS files are bad. Try an IPS file from the Hacks or Featured Hacks section of this site.

Credit goes to SMW Central