Opera Portable 37.0.2178.54

"Surprisingly, Opera [version 22] performed the best in the Octane 2.0 test, which measures how your browser will preform under the stress of games or highly interactive webpages." —Brandon Widder, DigitalTrends.com (November 25, 2014)

"Off-Road mode [previously called Turbo Mode] speeds up slow connections and reduces bandwidth." —Michael Muchmore, PCMag.com (date)

"One step away from MALWARE" —tuliphead (a user), download.CNET.com (March 20, 2015)

There are three variants of the Opera browser for Windows and Mac OS X. Each will run in parallel and can be installed side-by-side.

Opera

Opera is the product recommended for everyone. The quality requirements are tight and the stability is superb. The channel only receives small stability and security updates between the major releases.
   A major release happens approximately every two months.

Opera Beta

Opera beta is what will become our next main release. It contains the features we intend to ship at a quality level resembling what we intend to ship. No new features or significant changes are introduced between the major releases.
   The beta stream is what is often referee to, in development terms, as the testing stream.
   Opera beta was formerly known as Opera Next.

Opera Developer

Opera developer contains our latest changes. It is a nightly snapshot of our active development, delivered more or less as-is and minimal quality requirements.
   The intention is to showcase what we are working on and be open about upcoming changes to web technologies. It is not intended for daily browsing. It is provided for web developers (as the name suggests) and enthusiasts who are not afraid of some bumps in the road.
   The developer stream is what is often referred to, in development terms, as bleeding-edge or the unstable streams. Referring to the risk of suddenly getting cut by an unpolished developing feature.
   A Opera developer release happens approximately two times per week. (Thus, not recommended for users with limited bandwidth.) There can be fewer developer releases in the week preceding an Opera release.

OperaPortable_37.0.2178.54.paf
Size: 155 MB (162,816,000 bytes) Packed Size: 49.8 MB (52,285,440 bytes)
MD5: 10E56985071E036A488C4B73F07F9127
SHA-1: 891028A55868009252B726DF1E178AB7E3585A77

OperaBetaPortable_38.0.2220.25.paf
Size: 157 MB (165,650,432 bytes) Packed Size: 50.2 MB (52,695,040 bytes)
MD5: CCE9CAF2D0EE964D98CB96096E474D36
SHA-1: 008617ACB3E81118DA7BB8A870007DF3F8A04E4E

OperaDevPortable_39.0.2248.0.paf
Size: 160 MB (168,796,160 bytes) Packed Size: 50.8 MB (53,268,480 bytes)
MD5: DD129AD87E9FB06DE5ECE80F4D111794
SHA-1: C2284513C2D15462CE0FDEC5D0CBDABABA0A051A

Notes (included in the help.htm):
» You can get newer Flash player portable plugin (32/64-bit) build—both the NPAPI and PPAPI/pepperflash—at PCR’s notepad blog.
» More in the help.htm...[]