Effective August 1st, 2018 :OPTIONAL high speed data roaming for international (non Canada/Mexico) has changed to be $5 USD per day for up to 512MB of high speed data per day. This also includes unlimited inbound and outbound calls avoiding the 25c a min call charge. You can add this via 611 or this link: https://my.t-mobile.com/odf/DataPass:ALL - It is labeled as "24 Hour Global Pass". If that link doesn't works go to "Manage Data & Add Ons" in plan settings at http://my.t-mobile.com . A pass covers ANY countries in the given validity period - NOT just one country. So if you travel within multiple countries in the 24 hour period you get a max of 512MB of high speed data and unlimited calling across ALL countries prior to pass expiration. This is OPTIONAL and is not required, free 128Kb/sec or 256Kb/sec speeds are provided for users who don't pay for this extra data pack.

Effective July 15th, 2018: Calling rates for inbound and outbound calls were raised to 25c a min from the prior 20c a min when roaming internationally. You can buy a per Intl High Speed day pass for 512MB of high speed data that also includes calling at no cost during the validity of the pass.

Effective Feb 17, 2017: T-Mobile has bumped up speeds to 256Kb/sec for T-Mobile One users - this was FREE for a promotional period and required you to edit the lines with this plan to add the free or higher tier paid "T-Mobile One Plus" line item. The free line item is "T-Mobile One Plus promo" which will allow that line to be 256kb/sec and will also give 10GB of LTE North America hotspot tethering - The change can be done at my.t-mobile.com under plan for T-Mobile One customers or through 611. With the promotional period ended you can add the base $5 T-Mobile One Plus item to get 256Kb/sec

SUMMARY: T-Mobile USA on Simple Choice or newer plans (such as Select Choice) or T-Mobile One that list "Free International Roaming included" allow for free data and SMS in 210+ countries. Data and SMS is FREE; voice calls; inbound or outbound to any of the 210+ countries while roaming are 25 cents a min. Free data is NOT offered on T-Mobile essentials users outside of Canada/Mexico while SMS and 25c a min calls are still offered.

Canada and Mexico include FREE high speed roaming (HSPA or LTE full speed) as long as you are on the Simple Choice North America plan or a T-Mobile One plan. A monthly cap of 5GB for International High speed data in Canada and Mexico is now present - data will slow to lower speeds with no overage charges. Users on T-Mobile One Plus International are exempt from this 5GB cap.

You must be on a Postpaid plan, Prepay is NOT eligible nor is MetroPCS

NOTE: Devices with fully FREE data (e.g. 200MB free for tablets) and not on an additional plan are NOT eligible - switch those devices to a supported plan PRIOR to travel or you will be charged per MB fees.

WARNING: Highly suggest going to: https://my.t-mobile.com/profile.html (or login to my.t-mobile.com select profile), go to blocking and ensure "Block charge international roaming" is set to ON - keep "Ensure Block International Roaming" is set to OFF otherwise roaming will not work even in free data countries. This will ensure in countries where you are close to another country border that may NOT be part of free data roaming you will never be charged for data by ending up roaming on the adjacent country network if your phone is set to Automatic on networks.

WARNING FOR HIGH SPEED ADD ON $5 DATA PASS: Ensure you know your end date/time and heed the SMS warnings sent. You will be liable for 25c a min per call inbound or outbound if the pass expires and you do not activate another pass. Ensure you purchase another daily pass before making phone calls. As of Early August 2018, there was no method to purchase multiple days in a row.

T-Mobile FAQ:
http://support.t-mobile.com/docs/DOC-9455

Checklist for Roaming - follow this prior to leaving!:
http://support.t-mobile.com/docs/DOC-2182

Performance:
Speeds are throttled to 128Kb/sec on all supported plans, except for T-Mobile One Plus Add on (includes the Promo Feb 2017 T-Mobile One update with free One Plus Promo) which is 256Kb/sec. Connecting to the best network type possible will ensure you hitting these speeds limits (e.g. LTE). Performance is subject to the roaming carrier networks condition (is it congested or not) and how good the back-haul from the roaming carrier back to T-Mobile is. Reminder that T-Mobile Essentials users will have NO access to free data.

Filtering:
Your connection is terminated back to the US, so anything that works on T-Mobile US will continue to work. Example: China filters social media and Google services, using these services through your T-Mobile line won't experience this networking filtering. Local services in the country you are in MAY identify you as being in the US - any services that do IP geolocation will see that you are in the US.

Optional High Speed On Demand Data Passes with unlimited calling
If you want performance that is beyond the 128Kb/sec (or 256Kb/sec on T-Mobile One Plus Add ons) then a PAID optional high speed data pass removes the throttling performance limit. Effective Aug 2018 this pass is a $5 PER day for 512MB of high speed data (per day) and unlimited calling to allowed countries, waiving the 25c per min charge for inbound or outbound calls. To add, go to: https://my.t-mobile.com/odf/DataPass:ALL and add the "24 Hour Global Pass". If that link doesn't work add at http://my-t-mobile.com under Plan, "Manage Data & Add Ons" More information: http://support.t-mobile.com/docs/DOC-7261 NOTE: As of Early August 2018 you can only purchase one day at a time, so be cautious on expiration (Notified via SMS) to add another day pass to avoid getting charged 25c per phone call. A pass covers ANY countries in the given validity period - NOT just one country. So if you travel within multiple countries in the 24 hour period you get a max of 512MB of high speed data and unlimited calling across ALL countries prior to pass expiration.

Country search:
https://www.t-mobile.com/coverage/roaming

Country List at time of July 2018 update:
https://support.t-mobile.com/docs/DOC-37944

NOTE: there is no T-Mobile provided list of specific network roaming partners; you can call 611 and ask for a roaming specialist/tech and they can tell you per country roaming partners - we are attempting to capture working or problematic networks in this Wiki below also

Need Support while traveling? Read the hints below FIRST; then if support is needed call direct intl support for T-Mobile USA: +1-505-998-3793 [FREE CALL WHILE ROAMING] or if you cannot get Voice access use Skype or another service to dial.


Hints

#1 HINT: You MUST have Data roaming turned on - You will only see foreign networks on the network list - you will NOT see T-Mobile. Manually pick the networks from the list further below if you don't automatically connect.

- You do NOT have to pay for a high speed data package. 128Kb/sec (or 256Kb/sec on T-Mobile One Plus Add on) FREE throttled data is inclusive on all eligible postpaid plans

- High speed un-throttled data is also FREE for Canada and Mexico if you are on a Simple Choice North America plan or a T-Mobile One plan for up to 5GB of data per month (T-Mobile One Plus Intl users are not subject to the 5GB cap) . If you are not on these specific plans but on a legacy Simple Choice plan you will get standard 128Kb/sec FREE.

- For paid high speed packages, You can schedule WHEN optional high speed paid packages start (immediate or a time/date you set).

- On some accounts, High speed on demand data passes will will not be listed on my.t-mobile.com - under plans, "Manage Data & Add Ons". You can also contact customer care at 611 to add a data pass.

- If you purchase a package on phone or hotspot and are about to expire you can purchase ANOTHER one if you want and even though it will say "starts when your existing package date ends" it will IMMEDIATE activate it when you run out of data. Example You pay for 200Mb for one week and will eat into 200Mb, you can buy a package ANYTIME and it will future date it as being effective ONLY when the existing package date ends. HOWEVER once the existing package data amount is used up it will IMMEDIATE activate the paid pending package.

- On Demand Mifi WILL not roam at ALL if no package has ever been provisioned. Use the free data on your smartphone (or use another device with WiFi) and log into http://my.t-mobile.com Once logged in go to https://my-tmobile.com/Plan/Plans.as...vid=changeplan View plan for hotspot and and change plan, under Data Tab when viewing change plan add a package; once you confirm and submit (ENSURE before you submit you are adding to correct line!) you will get a confirmation. It was about 5 mins and then hotspot was able to connect to network.

- On demand Mifi WILL STOP working at end of time period NOT at end of data usage. So if you pick 500MB package which is 2 weeks expiration, it will actually STOP full speed at 500MB and revert to a 64Kb/sec speed till expiration; this ONLY applies to packages purchased on on demand hotspots. If you purchase a package for a smartphone you will revert to standard 128kb/sec

- Hotspots with On Demand will lose network access at end of paid period even if it reverted to lower hotspot only speed of 64kb/sec. So top up before you lose network.

- Legacy data match for tablets or hotspots (no longer offered but still allowed for current users) support 128Kb/sec on tablets and hotspots. If your data match plan details show match with North America added in the description then you get high speed in Canada and Mexico that uses your data match limit (up to 5GB) - after than you revert to 128Kb/sec. T-Mobile One Tablet will provide 128Kb/sec by default, if a T-Mobile One Plus add on is on that Tablet line (Including the free Feb 2017 One Plus Promo) speeds will be 256Kb/sec

- You can check current usage on any paid packages my viewing on the T-Mobile Application for Android or iOS or going to My T-Mobile website and filtering data usage on the line for International Data Roaming.

- When using a T-Mobile supported international data roaming plan on an iOS device internationally (in a nation on the 'free' list), you need to turn on Data Roaming on the iPhone/iPad Settings.

Troubleshooting

- If finding no networks when in new country, go to Airplane Mode - then back off Airplane mode and try again. If this fails to work FULLY power off phone and power back on. You may need to do a manual scan of networks on your device and pick one of the KNOWN networks below in the country list.

- If still not connecting to a network do ONE more phone reboot and attempt again.

- If you do connect to a network but are failing to get data, dial in your phone dialer #RON# (or try #ROF# FIRST then try #RON#). #RON# will turn intl roaming data on, #ROF# will turn it off. Sometimes cycling will cause a network to work.

- If connected to a network for Voice/SMS but still not getting data, set phone to Airplane mode ; wait till device is actually in airplane mode (15 sec or so); then take device off Airplane mode.

- If failing to get GSM/Voice/SMS services but you have data and phone shows "Emergency Calls Only" but data is working suggestion is to switch phone to 2G and connect to a network where you get data and voice/SMS. Once connected to that network switch phone back to 3G/Auto or LTE (or similar setting) and this may correct the issue. (Your mileage may vary)

- Try to change your APN to fast.t-mobile.com per the following guide, as an alternate you can try a temporary switch to epc.t-mobile.com - more details for APN change further below

- If none of these work, dial TMO Intl support +1-505-998-3793 (from another phone or Skype) and ask for "International Roaming Support" (make sure that is who they connect you to by asking the agent if they can help on a roaming support issue) - have them check your account is properly setup and eligible for International Roaming.


Countries with reported working networks supporting data
You can call support # below to ask for other networks. PLEASE share which networks works so we can always keep the Wiki up to date. Leave any comments with performance/quality to the "Problem Carriers section"

NOTE: If you have issues connecting turn off "Enable LTE" or LTE and do 3G/HSPA(4G) only. If you are still having issues to get data but can get voice dial Intl support +1-505-998-3793 (FREE CALL while roaming). If you cannot get any service, use another phone or Skype to dial this number.

Africa
Egypt: Vodafone, Elitsalat, Mobinil
Mauritius: EMTEL
South Africa: MTN, Vodacom, Telkom

Americas
Argentina: Movistar, Claro
Aruba: Digicel (May display as 363 02)
Bahamas: BTC
Barbados: Digicel
Bermuda: Digicel
Brazil: Tim, Vivo
Canada: Bell, Rogers (Some Provinces only), Telus, Freedom Mobile (former WIND), Videotron [HIGH SPEED INCLUDED ON SIMPLE CHOICE NORTH AMERICA]
Cayman Islands: Digicel
Chile: Movistar
Colombia: Telefonica Mobiles Colombia, Movistar
Costa Rica: Movistar, Claro
Dominican Republic: Claro, Orange, Viva
Ecuador: Claro, Movistar
El Salvador: Digicel, Movistar
Guatemala: Movistar
Honduras: Tigo
Jamaica: Digicel, Lime
México: Movistar, Telcel [HIGH SPEED INCLUDED ON SIMPLE CHOICE NORTH AMERICA]
Martinique: Digicel
Nicaragua: Mobinil, Movistar
Panama: Claro, Digicel
Perú: Movistar
St Kitts and Nevis: Digicel
St Lucia: Digicel
Sint Maarten (NL): Chippie (UTS)
Saint Martin (FR): Digicel
Turks and Caicos: Digicel
US Virgin Islands: Innovative (counts toward domestic roaming allowance)
Venezuela: Movistar

Asia Pacific
Australia: Telstra, Vodafone AU, OPTUS
Cambodia: CamGSM, Cellcard, Smart
China: China Mobile, China Unicom
Guam: Guam Telecom (Guam is considered outside the U.S. by T-Mobile)
Hong Kong: Smartone, Three
India: Airtel (Most Metro areas/regions), Vodafone
Indonesia (Bali): Indosat, Telkomsel
Japan: DOCOMO, Softbank
Macau: CTM, Three, Smartone
Malaysia: MAXIS
New Zealand: Vodafone, Spark NZ (no 2G), 2Degrees
Pakistan: Pak Telecom Mobile Limited (Ufone), Pakistan Mobile Company Limited (PMCL) (aka Mobilink), Telenor Pakistan, Warid Telecom
Philippines: Globe, SMART
Singapore: Starhub
South Korea: SKT, KT, Olleh
Sri Lanka: Mobitel
Taiwan: Taiwan Mobile
Thailand: AIS, DTAC
Vietnam: Viettel

Europe
Austria: Three, A1, T-Mobile Austria
Belgium: Orange (Mobistar), Proximus
Bulgaria: Telenor BG LTE is primary, saw A1 on 2g and Mtel on LTE very briefly
Czech Republic: Radiomobile/T-Mobile CZ, Vodafone CZ, O2
Denmark: 3 DK, Telenor DK
Faroe Islands: Foroya Tele
Finland: Elisa
France: Bouygues, Free, Orange, SFR
Germany: T-Mobile DE/Telekom.de, EPLUS
Greece: Cosmote
Hungary: T-Mobile
Iceland: Nova (LTE, better in cities), Siminn (3G only, better for rural)
Ireland: Vodafone, Three, Meteor
Italy: TIM, Wind, Vodafone IT
Luxembourg: Tango
Netherlands: KPN, T-Mobile, Vodafone
Norway: Telenor
Poland: T-Mobile
Portugal: MEO, NOS
Romania: Orange, Telekom, Vodafone
Russia: MTS Global
Spain: Movistar, Vodafone ES, Orange
Sweden: 3 SE
Switzerland: Orange, Swisscom
Turkey: Vodafone
UK: EE, Three, Vodafone
Ukraine: KYIVSTAR, MTS

Middle East/Near East
Bahrain: Viva / Batelco
Israel: Partner
Kuwait: Zain
Qatar: Ooredoo
UAE: Etisalat, du

LTE verified carriers:
MUST have a device supporting global LTE bands
- Argentina: Movistar
- Australia: Telstra (requires Band 3 / Band 28 device), OPTUS (5G)
- Bahamas: BTC
- Bahrain: Batelco
- Belgium: Proximus
- Canada: Bell, Rogers, Telus
- Chile: Movistar
- China: China Mobile (TD-LTE in some regions needs appropriate device or in some regions as LTE Band 3), China Unicom
- Colombia: Movistar
- Costa Rica: Movistar
- France: Orange, SFR
- Germany: T-Mobile DE/Telekom.de
- Guatemala: Movistar
- Hong Kong: Smartone
- Ireland: Vodafone
- Italy: TIM
- Japan: Docomo, Softbank
- Luxembourg: Tango
- Malaysia: MAXIS
- Mexico: Movistar
- Netherlands: T-Mobile NL, Vodafone
- Norway: Telenor
- Sinagapore: Starhub
- Sint Maarten (NL): Chippie (UTS)
- Spain: Orange
- Taiwan: Taiwan Mobile
- Thailand: AIS, DTAC
- UAE: du
- UK: EE, Vodafone (see footnote - NOT everywhere)

Problem carriers and LTE support notes
(Do not list carriers where you cannot get basic voice service)
- Argentina: Movistar (reports of poor performance), Claro (seemed much better, but difficult to gain initial connect/registration)
- Bermuda: Reports of getting UMTS (non HSPA 3G) only
- Canada: Wind performance seems better than other Canadian carriers (Your mileage may vary)
- China: China Mobile is 2G only unless you have a device supporting TD-SCDMA (3G) or TD-LTE Band 39/40/41. China Unicom roaming returned in April 2017
- Faroe Islands: Vodafone (Voice/SMS only, NO data service)
- Germany: Vodafone Germany (Voice/SMS only, NO data service in some regions)
- Hong Kong: Smartone, had to switch to 2G get access to network THEN switched phone back to 3G/Automatic if had problems getting access to network. Three: Reports of no longer working and only Smartone working
- Mauritius: Reports of issues connecting to Emtel sometimes - YMMV
- New Zealand: 2Degrees (limited coverage w/ reports of not working at all)
- Singapore: M1, SMS MAY require manually entering M1's SMSC +6596845999 if SMS doesn't work
- South Korea: SKT may require LTE to be disabled or conneciton may not be authenticated. Olleh/KT require multiple attempts to connect to network.
- UK: EE LTE roaming returned 1/21/17 - Reports of Vodafone LTE roaming in select parts of the UK only (not happening everywhere seems to be coverage challenged areas of EE only)
- Vietnam: Viettel